⚠️ Warning: This is a draft ⚠️

This means it might contain formatting issues, incorrect code, conceptual problems, or other severe issues.

If you want to help to improve and eventually enable this page, please fork RosettaGit's repository and open a merge request on GitHub.

;The game: Given an N by N square array of zeroes or ones in an initial configuration, and a target configuration of zeroes and ones The task is to transform one to the other in as few moves as possible by inverting whole numbered rows or whole lettered columns at once, as one move.

In an inversion any 1 becomes 0, and any 0 becomes 1 for that whole row or column.

;Task: Create a program to score for the Flipping bits game.

# The number of moves taken so far should be shown.

Show an example of a short game here, on this page, for a 3 by 3 array of bits.

This solution determines the size of the playground from the command line.

```with Ada.Text_IO, Ada.Command_Line, Ada.Numerics.Discrete_Random;

procedure Flip_Bits is

subtype Letter is Character range 'a' .. 'z';

Gen: Boolean_Rand.Generator;

type Matrix is array
(Letter range 'a' .. Last_Col, Positive range 1 .. Last_Row) of Boolean;

function Rand_Mat return Matrix is
M: Matrix;
begin
for I in M'Range(1) loop
for J in M'Range(2) loop
M(I,J) := Boolean_Rand.Random(Gen);
end loop;
end loop;
return M;
end Rand_Mat;

function Rand_Mat(Start: Matrix) return Matrix is
M: Matrix := Start;
begin
for I in M'Range(1) loop
if  Boolean_Rand.Random(Gen) then
for J in M'Range(2) loop
M(I,J) := not M(I, J);
end loop;
end if;
end loop;
for I in M'Range(2) loop
if  Boolean_Rand.Random(Gen) then
for J in M'Range(1) loop
M(J,I) := not M(J, I);
end loop;
end if;
end loop;
return M;
end Rand_Mat;

procedure Print(Message: String; Mat: Matrix) is
begin
for Ch in Matrix'Range(1) loop
end loop;
for I in Matrix'Range(2) loop
NIO.Put(I, Width => 3);
for Ch in Matrix'Range(1) loop
Ada.Text_IO.Put(if Mat(Ch, I) then " 1" else " 0");
end loop;
end loop;
end Print;

Current, Target: Matrix;
Moves: Natural := 0;

begin
-- choose random Target and start ("Current") matrices
Boolean_Rand.Reset(Gen);
Target := Rand_Mat;
loop
Current := Rand_Mat(Target);
exit when Current /= Target;
end loop;
Print("Target:", Target);

-- print and modify Current matrix, until it is identical to Target
while Current /= Target loop
Moves := Moves + 1;
Print("Current move #" & Natural'Image(Moves), Current);
Ada.Text_IO.Put_Line("Flip row 1 .." & Positive'Image(Last_Row) &
" or column 'a' .. '" & Last_Col & "'");
declare
function Let(S: String) return Character is (S(S'First));
function Val(Str: String) return Positive is (Positive'Value(Str));
begin
if Let(S) in 'a' .. Last_Col then
for I in Current'Range(2) loop
Current(Let(S), I) := not Current(Let(S), I);
end loop;
else
for I in Current'Range(1) loop
Current(I, Val(S)) := not Current(I, Val(S));
end loop;
end if;
end;
end loop;

-- summarize the outcome
Ada.Text_IO.Put_Line("Done after" & Natural'Image(Moves) & " Moves.");
end Flip_Bits;
```

{{out}}

For a 3*3-Matrix, the command line input is "c 3".

```>./flip_bits c 3

Target:
a b c
1 1 0 1
2 1 0 0
3 1 0 0

Current move # 1
a b c
1 1 0 0
2 1 0 1
3 0 1 0
Flip row 1 .. 3 or column 'a' .. 'c'
3

Current move # 2
a b c
1 1 0 0
2 1 0 1
3 1 0 1
Flip row 1 .. 3 or column 'a' .. 'c'
c
Done after 2 Moves.
```

## AutoHotkey

{{incomplete|AutoHotkey|Understood comment on why output is missing, but this is to make that fact more prominent.}} Uploads are currently disabled, so since a GUI is used, I can't show an example.

```size := 3 ; max 26
Loop, %size%
{
x := chr(A_Index+64)
If x = A
Loop, %size%
Gui, Add, Button, y+4 gFlip, % A_Index
Gui, Add, Button, ym gFlip, % x
Loop, %size%
{
y := A_Index
Random, %x%%y%, 0, 1
}
}
Loop, %size%
{
x := chr(A_Index+64)
Loop, %size%
{
y := A_Index
Gui, Add, Edit, % y=1 ? x="A" ? "xp+0 ym+30" : "x+14 ym+30" : "" . "ReadOnly vt" x y, % t%x%%y% := %x%%y%
}
}Gui, Add, Text, xp-18 ym w30 Right vMoves, % Moves:=1

; randomize
While (i < size)
{
Random, z, 1, %size%
Random, x, 0, 1
z := x ? chr(z+64) : z
Solution .= z ; to cheat
If Flip(z, size)
i := 0 ; ensure we are not at the solution
Else
i++ ; count
}
Gui, Show, NA
Return

Flip(z, size) {
Loop, %size%
{
If z is alpha
GuiControl, , %z%%A_Index%, % %z%%A_Index% := !%z%%A_Index%
Else
{
AIndex := chr(A_Index+64)
GuiControl, , %AIndex%%z%, % %AIndex%%z% := !%AIndex%%z%
}
}
Loop, %size%
{
x := chr(A_Index+64)
Loop, %size%
{
y := A_Index
If (%x%%y% != t%x%%y%)
Return 0
}
}
Return 1
}

Flip:
GuiControl, , Moves, % Moves++
If Flip(A_GuiControl, size)
{
Msgbox Success in %Moves% moves!
}
Return

ButtonO:
Return

GuiEscape:
GuiClose:
ExitApp
Return
```

## C

```
#include <stdio.h>
#include <stdlib.h>

int i, j;

void fliprow(int **b, int sz, int n)
{
for(i = 0; i < sz; i++)
b[n+1][i] = !b[n+1][i];
}

void flipcol(int **b, int sz, int n)
{
for(i = 1; i <= sz; i++)
b[i][n] = !b[i][n];
}

void initt(int **t, int sz)
{
for(i = 1; i <= sz; i++)
for(j = 0; j < sz; j++)
t[i][j] = rand()%2;
}

void initb(int **t, int **b, int sz)
{
for(i = 1; i <= sz; i++)
for(j = 0; j < sz; j++)
b[i][j] = t[i][j];

for(i = 1; i <= sz; i++)
fliprow(b, sz, rand()%sz+1);
for(i = 0; i < sz; i++)
flipcol(b, sz, rand()%sz);
}

void printb(int **b, int sz)
{
printf(" ");
for(i = 0; i < sz; i++)
printf(" %d", i);
printf("\n");

for(i = 1; i <= sz; i++)
{
printf("%d", i-1);
for(j = 0; j < sz; j++)
printf(" %d", b[i][j]);
printf("\n");
}

printf("\n");
}

int eq(int **t, int **b, int sz)
{
for(i = 1; i <= sz; i++)
for(j = 0; j < sz; j++)
if(b[i][j] != t[i][j])
return 0;
return 1;
}

void main()
{
int sz = 3;
int eql = 0;
int mov = 0;
int **t = malloc(sz*(sizeof(int)+1));
for(i = 1; i <= sz; i++)
t[i] = malloc(sz*sizeof(int));

int **b = malloc(sz*(sizeof(int)+1));
for(i = 1; i <= sz; i++)
b[i] = malloc(sz*sizeof(int));
char roc;
int n;
initt(t, sz);
initb(t, b, sz);

while(eq(t, b, sz))
initb(t, b, sz);

while(!eql)
{
printf("Target: \n");
printb(t, sz);
printf("Board: \n");
printb(b, sz);
printf("What to flip: ");
scanf(" %c", &roc);
scanf(" %d", &n);

switch(roc)
{
case 'r':
fliprow(b, sz, n);
break;
case 'c':
flipcol(b, sz, n);
break;
default:
perror("Please specify r or c and an number");
break;
}

printf("Moves Taken: %d\n", ++mov);

if(eq(t, b, sz))
{
printf("You win!\n");
eql = 1;
}
}
}

```

{{out}}

```
Target:
0 1 2
0 1 0 1
1 1 1 1
2 0 0 1

Board:
0 1 2
0 1 0 0
1 1 1 0
2 1 1 1

What to flip: r2
Moves Taken: 1
Target:
0 1 2
0 1 0 1
1 1 1 1
2 0 0 1

Board:
0 1 2
0 1 0 0
1 1 1 0
2 0 0 0

What to flip: c2
Moves Taken: 2
You win!

```

## C++

```
#include <time.h>
#include <iostream>
#include <string>

typedef unsigned char byte;
using namespace std;

class flip
{
public:
flip() { field = 0; target = 0; }
void play( int w, int h ) { wid = w; hei = h; createField(); gameLoop(); }

private:
void gameLoop()
{
int moves = 0;
while( !solved() )
{
display(); string r; cout << "Enter rows letters and/or column numbers: "; cin >> r;
for( string::iterator i = r.begin(); i != r.end(); i++ )
{
byte ii = ( *i );
if( ii - 1 >= '0' && ii - 1 <= '9' ) { flipCol( ii - '1' ); moves++; }
else if( ii >= 'a' && ii <= 'z' ) { flipRow( ii - 'a' ); moves++; }
}
}
cout << endl << endl << "** Well done! **" << endl << "Used " << moves << " moves." << endl << endl;
}

void display()
{ system( "cls" ); output( "TARGET:", target ); output( "YOU:", field ); }

void output( string t, byte* f )
{
cout << t << endl;
cout << " "; for( int x = 0; x < wid; x++ ) cout << " " << static_cast<char>( x + '1' ); cout << endl;
for( int y = 0; y < hei; y++ )
{
cout << static_cast<char>( y + 'a' ) << " ";
for( int x = 0; x < wid; x++ )
cout << static_cast<char>( f[x + y * wid] + 48 ) << " ";
cout << endl;
}
cout << endl << endl;
}

bool solved()
{
for( int y = 0; y < hei; y++ )
for( int x = 0; x < wid; x++ )
if( target[x + y * wid] != field[x + y * wid] ) return false;
return true;
}

void createTarget()
{
for( int y = 0; y < hei; y++ )
for( int x = 0; x < wid; x++ )
if( frnd() < .5f ) target[x + y * wid] = 1;
else target[x + y * wid] = 0;
memcpy( field, target, wid * hei );
}

void flipCol( int c )
{ for( int x = 0; x < hei; x++ ) field[c + x * wid] = !field[c + x * wid]; }

void flipRow( int r )
{ for( int x = 0; x < wid; x++ ) field[x + r * wid] = !field[x + r * wid]; }

void calcStartPos()
{
int flips = ( rand() % wid + wid + rand() % hei + hei ) >> 1;
for( int x = 0; x < flips; x++ )
{ if( frnd() < .5f ) flipCol( rand() % wid ); else flipRow( rand() % hei ); }
}

void createField()
{
if( field ){ delete [] field; delete [] target; }
int t = wid * hei; field = new byte[t]; target = new byte[t];
memset( field, 0, t ); memset( target, 0, t ); createTarget();
while( true ) { calcStartPos(); if( !solved() ) break; }
}

float frnd() { return static_cast<float>( rand() ) / static_cast<float>( RAND_MAX ); }

byte* field, *target; int wid, hei;
};

int main( int argc, char* argv[] )
{ srand( time( NULL ) ); flip g; g.play( 3, 3 ); return system( "pause" ); }

```

{{out}}

```
TARGET:
1 2 3
a 0 1 0
b 0 1 0
c 0 1 0

YOU:
1 2 3
a 0 0 0
b 0 0 0
c 1 1 1

Enter rows letters and/or column numbers: 2c

** Well done! **
Used 2 moves.

```

## Clojure

```(defn cols [board]
(mapv vec (apply map list board)))

(defn flipv [v]
(mapv #(if (> % 0) 0 1) v))

(defn flip-row [board n]
(assoc board n (flipv (get board n))))

(defn flip-col [board n]
(cols (flip-row (cols board) n)))

(defn play-rand [board n]
(if (= n 0)
board
(let [f (if (= (rand-int 2) 0) flip-row flip-col)]
(recur (f board (rand-int (count board))) (dec n)))))

(defn rand-binary-vec [size]
(vec (take size (repeatedly #(rand-int 2)))))

(defn rand-binary-board [size]
(vec (take size (repeatedly #(rand-binary-vec size)))))

(defn numbers->letters [coll]
(map #(char (+ 97 %)) coll))

(defn column-labels [size]
(apply str (interpose " " (numbers->letters (range size)))))

(defn print-board [board]
(let [size (count board)]
(println "\t " (column-labels size))
(dotimes [n size] (println (inc n) "\t" (board n)))))

(defn key->move [key]
(let [start (int (first key))
row-value (try (Long/valueOf key) (catch NumberFormatException e))]
(cond
(<= 97 start 122) [:col (- start 97)]
(<= 65 start 90) [:col (- start 65)]
(> row-value 0) [:row (dec row-value)]
:else nil)))

(defn play-game [target-board current-board n]
(println "\nTurn " n)
(print-board current-board)
(if (= target-board current-board)
(println "You win!")
axis (first move)
idx (second move)]
(cond
(= axis :row) (play-game target-board (flip-row current-board idx) (inc n))
(= axis :col) (play-game target-board (flip-col current-board idx) (inc n))
:else (println "Quitting!")))))

(defn -main
"Flip the Bits Game!"
[& args]
(if-not (empty? args)
(let [target-board (rand-binary-board (Long/valueOf (first args)))]
(println "Target")
(print-board target-board)
(play-game target-board (play-rand target-board 3) 0))))
```

{{out}}

```
Target
a b c
1        [1 0 1]
2        [0 1 1]
3        [0 1 1]

Turn  0
a b c
1        [1 0 1]
2        [0 1 1]
3        [1 0 0]
3

Turn  1
a b c
1        [1 0 1]
2        [0 1 1]
3        [0 1 1]
You win!

```

## D

{{trans|Python}}

```import std.stdio, std.random, std.ascii, std.string, std.range,
std.algorithm, std.conv;

enum N = 3; // Board side.
static assert(N <= lowercase.length);
enum columnIDs = lowercase[0 .. N];
alias Board = ubyte[N][N];

void flipBits(ref Board board, in size_t count=1) {
foreach (immutable _; 0 .. count)
board[uniform(0, \$)][uniform(0, \$)] ^= 1;
}

void notRow(ref Board board, in size_t i) pure nothrow {
board[i][] ^= 1;
}

void notColumn(ref Board board, in size_t i) pure nothrow {
foreach (ref row; board)
row[i] ^= 1;
}

Board generateGameBoard(in ref Board target) {
// board is generated with many flips, to keep parity unchanged.
Board board = target;
while (board == target)
foreach (immutable _; 0 .. 2 * N)
[&notRow, &notColumn][uniform(0, 2)](board, uniform(0, N));
return board;
}

void show(in ref Board board, in string comment) {
comment.writeln;
writefln("     %-(%c %)", columnIDs);
foreach (immutable j, const row; board)
writefln("  %2d %-(%d %)", j + 1, row);
}

void main() {
"T prints the target, and Q exits.\n".writeln;
// Create target and flip some of its bits randomly.
Board target;
flipBits(target, uniform(0, N) + 1);
show(target, "Target configuration is:");

auto board = generateGameBoard(target);
immutable prompt = format("  1-%d / %s-%s to flip, or T, Q: ",
N, columnIDs[0], columnIDs.back);
uint move = 1;
while (board != target) {
show(board, format("\nMove %d:", move));
prompt.write;

if (ans.length == 1 && columnIDs.canFind(ans)) {
board.notColumn(columnIDs.countUntil(ans));
move++;
} else if (iota(1, N + 1).map!text.canFind(ans)) {
board.notRow(ans.to!uint - 1);
move++;
} else if (ans == "T") {
show(target, "Target configuration is:");
} else if (ans == "Q") {
return "Game stopped.".writeln;
} else
writefln("  Wrong input '%s'. Try again.\n", ans.take(9));
}

"\nWell done!".writeln;
}
```

{{out}}

```T prints the target, and Q exits.

Target configuration is:
a b c
1 1 1 1
2 0 0 0
3 0 0 0

Move 1:
a b c
1 1 0 0
2 1 0 0
3 1 0 0
1-3 / a-c to flip, or T, Q: a

Move 2:
a b c
1 0 0 0
2 0 0 0
3 0 0 0
1-3 / a-c to flip, or T, Q: 1

Well done!
```

## Elixir

{{works with|Elixir|1.1}} {{trans|Ruby}}

```defmodule Flip_game do
@az  Enum.map(?a..?z, &List.to_string([&1]))
@in2i Enum.concat(Enum.map(1..26, fn i -> {to_string(i), i} end),
Enum.with_index(@az) |> Enum.map(fn {c,i} -> {c,-i-1} end))
|> Enum.into(Map.new)

def play(n) when n>2 do
target = generate_target(n)
display(n, "Target: ", target)
board = starting_config(n, target)
play(n, target, board, 1)
end

def play(n, target, board, moves) do
display(n, "Board: ", board)
ans = IO.gets("row/column to flip: ") |> String.strip |> String.downcase
new_board = case @in2i[ans] do
i when i in 1..n   -> flip_row(n, board, i)
i when i in -1..-n -> flip_column(n, board, -i)
_ -> IO.puts "invalid input: #{ans}"
board
end
if target == new_board do
display(n, "Board: ", new_board)
IO.puts "You solved the game in #{moves} moves"
else
IO.puts ""
play(n, target, new_board, moves+1)
end
end

defp generate_target(n) do
for i <- 1..n, j <- 1..n, into: Map.new, do: {{i, j}, :rand.uniform(2)-1}
end

defp starting_config(n, target) do
Enum.concat(1..n, -1..-n)
|> Enum.take_random(n)
|> Enum.reduce(target, fn x,acc ->
if x>0, do: flip_row(n, acc, x),
else: flip_column(n, acc, -x)
end)
end

defp flip_row(n, board, row) do
Enum.reduce(1..n, board, fn col,acc ->
Map.update!(acc, {row,col}, fn bit -> 1 - bit end)
end)
end

defp flip_column(n, board, col) do
Enum.reduce(1..n, board, fn row,acc ->
Map.update!(acc, {row,col}, fn bit -> 1 - bit end)
end)
end

defp display(n, title, board) do
IO.puts title
IO.puts "   #{Enum.join(Enum.take(@az,n), " ")}"
Enum.each(1..n, fn row ->
:io.fwrite "~2w ", [row]
IO.puts Enum.map_join(1..n, " ", fn col -> board[{row, col}] end)
end)
end
end

Flip_game.play(3)
```

{{out}}

```
Target:
a b c
1 1 0 1
2 0 1 1
3 0 1 1
Board:
a b c
1 0 1 1
2 0 1 0
3 1 0 1
row/column to flip: 2

Board:
a b c
1 0 1 1
2 1 0 1
3 1 0 1
row/column to flip: a

Board:
a b c
1 1 1 1
2 0 0 1
3 0 0 1
row/column to flip: b
Board:
a b c
1 1 0 1
2 0 1 1
3 0 1 1
You solved the game in 3 moves

```

## Fortran

This version uses some routines (like rand(), srand() and date_and_time()) from the GNU Fortran compiler. Formats are used to print data on the screen in an appropriate manner. The number of rows (or columns) is a variable and the current implementation allows for any number between 1 and 10. Incorrect inputs are also verified.

```
!Implemented by Anant Dixit (October 2014)
program flipping_bits
implicit none
character(len=*), parameter :: cfmt = "(A3)", ifmt = "(I3)"
integer :: N, i, j, io, seed(8), moves, input
logical, allocatable :: Brd(:,:), Trgt(:,:)
logical :: solved
double precision :: r

do
write(*,*) 'Enter the number of squares (between 1 and 10) you would like: '
if(N.gt.0 .and. N.le.10 .and. io.eq.0) exit
write(*,*) 'Please, an integer between 1 and 10'
end do

allocate(Brd(N,N),Trgt(N,N))
call date_and_time(values=seed)
call srand(1000*seed(7)+seed(8)+60000*seed(6))
do i = 1,N
do j = 1,N
r = rand()
if(r.gt.0.5D0) then
Brd(i,j) = .TRUE.
Trgt(i,j) = .TRUE.
else
Brd(i,j) = .FALSE.
Trgt(i,j) = .FALSE.
end if
end do
end do
! Random moves taken by the program to `create' a target
moves = N
do i = 1,moves
r = 1+2.0D0*dble(N)*rand() - 1.0D-17 !Only to make sure that the number is between 1 and 2N (less than 2N-1)
if(floor(r).le.N) then
do j = 1,N
Trgt(floor(r),j) = .NOT.Trgt(floor(r),j)
end do
else
r = r-N
do j = 1,N
Trgt(j,floor(r)) = .NOT.Trgt(j,floor(r))
end do
end if
end do

!This part checks if the target and the starting configurations are same or not.
do
input = N
call next_move(Brd,Trgt,N,input,solved)
call next_move(Brd,Trgt,N,input,solved)
if(solved) then
r = 1+2.0D0*dble(N)*rand() - 1.0D-17
if(floor(r).le.N) then
do j = 1,N
Trgt(floor(r),j) = .NOT.Trgt(floor(r),j)
end do
else
r = r-N
do j = 1,N
Trgt(j,floor(r)) = .NOT.Trgt(j,floor(r))
end do
end if
else
exit
end if
end do

write(*,*) 'Welcome to the Flipping Bits game!'
write(*,*) 'You have the current position'

moves = 0
call display(Brd,Trgt,N)
input = N
do
write(*,*) 'Number of moves so far:', moves
write(*,*) 'Select the column or row you wish to flip: '
if(io.eq.0 .and. input.gt.0 .and. input.le.(2*N)) then
moves = moves+1
write(*,*) 'Flipping ', input
call next_move(Brd,Trgt,N,input,solved)
call display(Brd,Trgt,N)
if(solved) exit
else
write(*,*) 'Please enter a valid column or row number. To quit, press Ctrl+C!'
end if
end do

write(*,*) 'Congratulations! You finished the game!'
write(*,*) ' moves were taken by you!!'
deallocate(Brd,Trgt)
end program

subroutine display(Brd,Trgt,N)
implicit none
!arguments
integer :: N
logical :: Brd(N,N), Trgt(N,N)
!local
character(len=*), parameter :: cfmt = "(A3)", ifmt = "(I3)"
integer :: i, j
write(*,*) 'Current Configuration: '
do i = 0,N
if(i.eq.0) then
else
end if
end do
write(*,*)
do i = 0,N
if(i.eq.0) then
do j = 0,N+2
end do
else
do j = 1,N
if(Brd(i,j)) then
else
end if
end do
end if
write(*,*)
end do

write(*,*)
write(*,*)

write(*,*) 'Target Configuration'
do i = 0,N
if(i.eq.0) then
else
end if
end do
write(*,*)
do i = 0,N
if(i.eq.0) then
do j = 0,N+2
end do
else
do j = 1,N
if(Trgt(i,j)) then
else
end if
end do
end if
write(*,*)
end do
write(*,*)
write(*,*)
end subroutine

subroutine next_move(Brd,Trgt,N,input,solved)
implicit none
!arguments
integer :: N, input
logical :: Brd(N,N), Trgt(N,N), solved
!others
integer :: i,j

if(input.gt.N) then
input = input-N
do i = 1,N
Brd(input,i) = .not.Brd(input,i)
end do
else
do i = 1,N
Brd(i,input) = .not.Brd(i,input)
end do
end if
solved = .TRUE.
do i = 1,N
do j = 1,N
if( (.not.Brd(i,j).and.Trgt(i,j)) .or. (Brd(i,j).and..not.Trgt(i,j)) ) then
solved = .FALSE.
exit
end if
end do
if(.not.solved) exit
end do
end subroutine

```

Example:

```
./flipping_bits
Enter the number of squares (between 1 and 10) you would like:
3
Welcome to the Flipping Bits game!
You have the current position
Current Configuration:
R/C |   1  2  3
------------
4 |   1  0  0
5 |   1  1  0
6 |   0  0  0

Target Configuration
R/C |   1  2  3
------------
4 |   1  1  1
5 |   1  0  1
6 |   1  0  0

Select the column or row you wish to flip:
2
Current Configuration:
R/C |   1  2  3
------------
4 |   1  1  0
5 |   1  0  0
6 |   0  1  0

Target Configuration
R/C |   1  2  3
------------
4 |   1  1  1
5 |   1  0  1
6 |   1  0  0

Select the column or row you wish to flip:
3
Current Configuration:
R/C |   1  2  3
------------
4 |   1  1  1
5 |   1  0  1
6 |   0  1  1

Target Configuration
R/C |   1  2  3
------------
4 |   1  1  1
5 |   1  0  1
6 |   1  0  0

Select the column or row you wish to flip:
6
Current Configuration:
R/C |   1  2  3
------------
4 |   1  1  1
5 |   1  0  1
6 |   1  0  0

Target Configuration
R/C |   1  2  3
------------
4 |   1  1  1
5 |   1  0  1
6 |   1  0  0

Congratulations! You finished the game!
3  moves were taken by you!!

```

## Go

```package main

import (
"fmt"
"math/rand"
"time"
)

func main() {

rand.Seed(time.Now().UnixNano())

var n int = 3 // Change to define board size
var moves int = 0

a := make([][]int, n)
for i := range a {
a[i] = make([]int, n)
for j := range a {
a[i][j] = rand.Intn(2)
}
}

b := make([][]int, len(a))
for i := range a {
b[i] = make([]int, len(a[i]))
copy(b[i], a[i])
}

for i := rand.Intn(100); i > 0 || compareSlices(a, b) == true; i-- {
b = flipCol(b, rand.Intn(n) + 1)
b = flipRow(b, rand.Intn(n) + 1)
}

fmt.Println("Target:")
drawBoard(a)
fmt.Println("\nBoard:")
drawBoard(b)

var rc rune
var num int

for {
for{
fmt.Printf("\nFlip row (r) or column (c)  1 .. %d (c1, ...): ", n)
_, err := fmt.Scanf("%c%d", &rc, &num)
if err != nil {
fmt.Println(err)
continue
}
if num < 1 || num > n {
fmt.Println("Wrong command!")
continue
}
break
}

switch rc {
case 'c':
fmt.Printf("Column %v will be flipped\n", num)
flipCol(b, num)
case 'r':
fmt.Printf("Row %v will be flipped\n", num)
flipRow(b, num)
default:
fmt.Println("Wrong command!")
continue
}

moves++
fmt.Println("\nMoves taken: ", moves)

fmt.Println("Target:")
drawBoard(a)
fmt.Println("\nBoard:")
drawBoard(b)

if compareSlices(a, b) {
fmt.Printf("Finished. You win with %d moves!\n", moves)
break
}
}
}

func drawBoard (m [][]int) {
fmt.Print("   ")
for i := range m {
fmt.Printf("%d ", i+1)
}
for i := range m {
fmt.Println()
fmt.Printf("%d ", i+1)
for _, val := range m[i] {
fmt.Printf(" %d", val)
}
}
fmt.Print("\n")
}

func flipRow(m [][]int, row int) ([][]int) {
for j := range m {
m[row-1][j] ^= 1
}
return m
}

func flipCol(m [][]int, col int) ([][]int) {
for j := range m {
m[j][col-1] ^= 1
}
return m
}

func compareSlices(m [][]int, n[][]int) bool {
o := true
for i := range m {
for j := range m {
if m[i][j] != n[i][j] { o = false }
}
}
return o
}
```

{{out}}

```
Target:
1 2 3
1  0 1 1
2  0 1 1
3  1 1 1

Board:
1 2 3
1  1 0 0
2  1 0 0
3  1 1 1

Flip row (r) or column (c)  1 .. 3 (c1, ...): r1
Row 1 will be flipped

Moves taken:  1
Target:
1 2 3
1  0 1 1
2  0 1 1
3  1 1 1

Board:
1 2 3
1  0 1 1
2  1 0 0
3  1 1 1

Flip row (r) or column (c)  1 .. 3 (c1, ...): r2
Row 2 will be flipped

Moves taken:  2
Target:
1 2 3
1  0 1 1
2  0 1 1
3  1 1 1

Board:
1 2 3
1  0 1 1
2  0 1 1
3  1 1 1
Finished. You win with 2 moves!
```

Maximum game size is 9x9 because the array indices are the characters 1 until 9.

```import Data.List (intersperse)

import System.Random (randomRIO)

import Data.Array (Array, (!), (//), array, bounds)

import Control.Monad (zipWithM_, replicateM, foldM, when)

type Board = Array (Char, Char) Int

flp :: Int -> Int
flp 0 = 1
flp 1 = 0

numRows, numCols :: Board -> String
numRows t =
let ((a, _), (b, _)) = bounds t
in [a .. b]

numCols t =
let ((_, a), (_, b)) = bounds t
in [a .. b]

flipRow, flipCol :: Board -> Char -> Board
flipRow t r =
let e =
[ (ix, flp (t ! ix))
| ix <- zip (repeat r) (numCols t) ]
in t // e

flipCol t c =
let e =
[ (ix, flp (t ! ix))
| ix <- zip (numRows t) (repeat c) ]
in t // e

printBoard :: Board -> IO ()
printBoard t = do
let rows = numRows t
cols = numCols t
f 0 = '0'
f 1 = '1'
p r xs = putStrLn \$ [r, ' '] ++ intersperse ' ' (map f xs)
putStrLn \$ "  " ++ intersperse ' ' cols
zipWithM_
p
rows
[ [ t ! (y, x)
| x <- cols ]
| y <- rows ]

-- create a random goal board, and flip rows and columns randomly
-- to get a starting board
setupGame :: Char -> Char -> IO (Board, Board)
setupGame sizey sizex
-- random cell value at (row, col)
= do
let mk rc = (\v -> (rc, v)) <\$> randomRIO (0, 1)
rows = ['a' .. sizey]
cols = ['1' .. sizex]
goal <-
array (('a', '1'), (sizey, sizex)) <\$>
mapM
mk
[ (r, c)
| r <- rows
, c <- cols ]
start <-
do let change :: Board -> Int -> IO Board
-- flip random row
change t 0 = flipRow t <\$> randomRIO ('a', sizey)
-- flip random col
change t 1 = flipCol t <\$> randomRIO ('1', sizex)
numMoves <- randomRIO (3, 15) -- how many flips (3 - 15)
-- determine if rows or cols are flipped
moves <- replicateM numMoves \$ randomRIO (0, 1)
-- make changes and get a starting board
foldM change goal moves
if goal /= start -- check if boards are different
then return (goal, start) -- all ok, return both boards
else setupGame sizey sizex -- try again

main :: IO ()
main = do
putStrLn "Select a board size (1 - 9).\nPress any other key to exit."
sizec <- getChar
when (sizec `elem` ['1' .. '9']) \$
do let size = read [sizec] - 1
(g, s) <- setupGame (['a' ..] !! size) (['1' ..] !! size)
turns g s 0
where
turns goal current moves = do
putStrLn "\nGoal:"
printBoard goal
putStrLn "\nBoard:"
printBoard current
when (moves > 0) \$
putStrLn \$ "\nYou've made " ++ show moves ++ " moves so far."
putStrLn \$
"\nFlip a row (" ++
numRows current ++ ") or a column (" ++ numCols current ++ ")"
v <- getChar
if v `elem` numRows current
then check \$ flipRow current v
else if v `elem` numCols current
then check \$ flipCol current v
else tryAgain
where
check t =
if t == goal
then putStrLn \$ "\nYou've won in " ++ show (moves + 1) ++ " moves!"
else turns goal t (moves + 1)
tryAgain = do
putStrLn ": Invalid row or column."
turns goal current moves
```

{{Out}}

```Select a board size (1 - 9).
Press any other key to exit.
3
Goal:
1 2 3
a 1 1 0
b 1 0 0
c 0 0 0

Board:
1 2 3
a 1 0 0
b 1 1 0
c 1 0 1

Flip a row (abc) or a column (123)
2
Goal:
1 2 3
a 1 1 0
b 1 0 0
c 0 0 0

Board:
1 2 3
a 1 1 0
b 1 0 0
c 1 1 1

You've made 1 moves so far.

Flip a row (abc) or a column (123)
c
You've won in 2 moves!
```

## J

Using J's command line as the game ui:

```start=:3 :0
Moves=:0
N=:i.y
Board=: ?2\$~,~y
'fr fc'=. (2,y)\$}.#:(+?&.<:@<:)2x^2*y
End=: fr~:fc~:"1 Board
Board;End
)

abc=:'abcdefghij'
move=:3 :0
fc=. N e.abc i. y ([-.-.)abc
fr=. N e._-.~_ "."0 abc-.~":y
Board=: fr~:fc~:"1 Board
smoutput (":Moves=:Moves++/fr,fc),' moves'
if. Board-:End do.
'yes'
else.
Board;End
end.
)
```

Example:

```   start 3
┌─────┬─────┐
│1 1 1│1 0 1│
│1 1 0│0 1 1│
│1 0 0│0 0 1│
└─────┴─────┘
move 'b2'
2 moves
┌─────┬─────┐
│1 0 1│1 0 1│
│1 0 0│0 1 1│
│0 0 1│0 0 1│
└─────┴─────┘
move '1'
3 moves
yes
```

Note that any size game may be generated but this version only recognizes column flips for the first ten columns.

## Java

[[File:Flipping_bits_java.gif|200px|thumb|right]] {{works with|Java|8}}

```import java.awt.*;
import java.awt.event.*;
import java.util.*;
import javax.swing.*;

public class FlippingBitsGame extends JPanel {
final int maxLevel = 7;
final int minLevel = 3;

private Random rand = new Random();
private int[][] grid, target;
private Rectangle box;
private int n = maxLevel;
private boolean solved = true;

FlippingBitsGame() {
setPreferredSize(new Dimension(640, 640));
setBackground(Color.white);
setFont(new Font("SansSerif", Font.PLAIN, 18));

box = new Rectangle(120, 90, 400, 400);

startNewGame();

@Override
public void mousePressed(MouseEvent e) {
if (solved) {
startNewGame();
} else {
int x = e.getX();
int y = e.getY();

if (box.contains(x, y))
return;

if (x > box.x && x < box.x + box.width) {
flipCol((x - box.x) / (box.width / n));

} else if (y > box.y && y < box.y + box.height)
flipRow((y - box.y) / (box.height / n));

if (solved(grid, target))
solved = true;

printGrid(solved ? "Solved!" : "The board", grid);
}
repaint();
}
});
}

void startNewGame() {
if (solved) {

n = (n == maxLevel) ? minLevel : n + 1;

grid = new int[n][n];
target = new int[n][n];

do {
shuffle();

for (int i = 0; i < n; i++)
target[i] = Arrays.copyOf(grid[i], n);

shuffle();

} while (solved(grid, target));

solved = false;
printGrid("The target", target);
printGrid("The board", grid);
}
}

void printGrid(String msg, int[][] g) {
System.out.println(msg);
for (int[] row : g)
System.out.println(Arrays.toString(row));
System.out.println();
}

boolean solved(int[][] a, int[][] b) {
for (int i = 0; i < n; i++)
if (!Arrays.equals(a[i], b[i]))
return false;
return true;
}

void shuffle() {
for (int i = 0; i < n * n; i++) {
if (rand.nextBoolean())
flipRow(rand.nextInt(n));
else
flipCol(rand.nextInt(n));
}
}

void flipRow(int r) {
for (int c = 0; c < n; c++) {
grid[r][c] ^= 1;
}
}

void flipCol(int c) {
for (int[] row : grid) {
row[c] ^= 1;
}
}

void drawGrid(Graphics2D g) {
g.setColor(getForeground());

if (solved)
else
g.drawString("Click next to a row or a column to flip.", 170, 600);

int size = box.width / n;

for (int r = 0; r < n; r++)
for (int c = 0; c < n; c++) {
g.setColor(grid[r][c] == 1 ? Color.blue : Color.orange);
g.fillRect(box.x + c * size, box.y + r * size, size, size);
g.setColor(getBackground());
g.drawRect(box.x + c * size, box.y + r * size, size, size);
g.setColor(target[r][c] == 1 ? Color.blue : Color.orange);
g.fillRect(7 + box.x + c * size, 7 + box.y + r * size, 10, 10);
}
}

@Override
public void paintComponent(Graphics gg) {
super.paintComponent(gg);
Graphics2D g = (Graphics2D) gg;
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING,
RenderingHints.VALUE_ANTIALIAS_ON);

drawGrid(g);
}

public static void main(String[] args) {
SwingUtilities.invokeLater(() -> {
JFrame f = new JFrame();
f.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
f.setTitle("Flipping Bits Game");
f.setResizable(false);
f.pack();
f.setLocationRelativeTo(null);
f.setVisible(true);
});
}
}
```
```The target
[0, 1, 0]
[0, 1, 0]
[0, 1, 0]

The board
[0, 1, 1]
[0, 1, 1]
[0, 1, 1]

Solved!
[0, 1, 0]
[0, 1, 0]
[0, 1, 0]
```

## JavaScript

```function numOfRows(board) { return board.length; }
function numOfCols(board) { return board[0].length; }
function boardToString(board) {
for (var c = 0; c < numOfCols(board); c++)
header += c + ' ';

// Then the side-header + board
var sideboard = [];
for (var r = 0; r < numOfRows(board); r++) {
sideboard.push(r + ' [' + board[r].join(' ') + ']');
}

return header + '\n' + sideboard.join('\n');
}
function flipRow(board, row) {
for (var c = 0; c < numOfCols(board); c++) {
board[row][c] = 1 - board[row][c];
}
}
function flipCol(board, col) {
for (var r = 0; r < numOfRows(board); r++) {
board[r][col] = 1 - board[r][col];
}
}

function playFlippingBitsGame(rows, cols) {
rows = rows | 3;
cols = cols | 3;
var targetBoard = [];
var manipulatedBoard = [];
// Randomly generate two identical boards.
for (var r = 0; r < rows; r++) {
targetBoard.push([]);
manipulatedBoard.push([]);
for (var c = 0; c < cols; c++) {
targetBoard[r].push(Math.floor(Math.random() * 2));
manipulatedBoard[r].push(targetBoard[r][c]);
}
}
// Naive-scramble one of the boards.
while (boardToString(targetBoard) == boardToString(manipulatedBoard)) {
var scrambles = rows * cols;
while (scrambles-- > 0) {
if (0 == Math.floor(Math.random() * 2)) {
flipRow(manipulatedBoard, Math.floor(Math.random() * rows));
}
else {
flipCol(manipulatedBoard, Math.floor(Math.random() * cols));
}
}
}
// Get the user to solve.
'Try to match both boards.\n' +
'Enter `r<num>` or `c<num>` to manipulate a row or col or enter `q` to quit.'
);
var input = '', letter, num, moves = 0;
while (boardToString(targetBoard) != boardToString(manipulatedBoard) && input != 'q') {
input = prompt(
'Target:\n' + boardToString(targetBoard) +
'\n\n\n' +
'Board:\n' + boardToString(manipulatedBoard)
);
try {
letter = input.charAt(0);
num = parseInt(input.slice(1));
if (letter == 'q')
break;
if (isNaN(num)
|| (letter != 'r' && letter != 'c')
|| (letter == 'r' && num >= rows)
|| (letter == 'c' && num >= cols)
) {
throw new Error('');
}
if (letter == 'r') {
flipRow(manipulatedBoard, num);
}
else {
flipCol(manipulatedBoard, num);
}
moves++;
}
catch(e) {
alert('Uh-oh, there seems to have been an input error');
}
}
if (input == 'q') {
}
else {
alert('Completed in ' + moves + ' moves.');
}
}
```
```Try to match both boards.
Enter `r<num>` or `c<num>` to manipulate a row or col or enter `q` to quit.

Target:
0 1 2
0 [0 1 1]
1 [1 0 0]
2 [1 0 1]

Board:
0 1 2
0 [0 0 0]
1 [1 1 1]
2 [0 0 1]
r2

Target:
0 1 2
0 [0 1 1]
1 [1 0 0]
2 [1 0 1]

Board:
0 1 2
0 [0 0 0]
1 [0 0 0]
2 [0 0 1]
c0

Target:
0 1 2
0 [0 1 1]
1 [1 0 0]
2 [1 0 1]

Board:
0 1 2
0 [1 0 0]
1 [1 0 0]
2 [1 0 1]
r0

Completed in 3 moves.
```

## Julia

```module FlippingBitsGame

using Printf, Random
import Base.size, Base.show, Base.==

struct Configuration
M::BitMatrix
end

Base.size(c::Configuration) = size(c.M)
function Base.show(io::IO, conf::Configuration)
M = conf.M
nrow, ncol = size(M)
print(io, " " ^ 3)
for c in 1:ncol
@printf(io, "%3i", c)
end
println(io, "\n", " " ^ 4, "-" ^ 3ncol)
for r in 1:nrow
@printf(io, "%2i |", r)
for c in 1:ncol
@printf(io, "%2c ", ifelse(M[r, c], 'T', 'F'))
end
println(io)
end
return nothing
end
Base.:(==)(a::Configuration, b::Configuration) = a.M == b.M

struct Index{D}
i::Int
end
const ColIndex = Index{:C}
const RowIndex = Index{:R}

function flipbits!(conf::Configuration, c::ColIndex)
col = @view conf.M[:, c.i]
@. col = !col
return conf
end
function flipbits!(conf::Configuration, r::RowIndex)
row = @view conf.M[r.i, :]
@. row = !row
return conf
end

randomconfig(nrow::Integer, ncol::Integer) = Configuration(bitrand(nrow, ncol))

function randommoves!(conf::Configuration, nflips::Integer)
nrow, ncol = size(conf)
for _ in Base.OneTo(nflips)
if rand() < 0.5
flipbits!(conf, ColIndex(rand(1:ncol)))
else
flipbits!(conf, RowIndex(rand(1:nrow)))
end
end
return conf
end

function play()
nrow::Int, ncol::Int = 0, 0
while nrow < 2 || ncol < 2
print("Insert the size of the matrix (nrow [> 1] *space* ncol [> 1]):")
end
mat = randomconfig(nrow, ncol)
obj = deepcopy(mat)
randommoves!(obj, 100)
nflips = 0
while mat != obj
println("\n", nflips, " flips until now.")
println("Current configuration:")
println(mat)
println("Objective configuration:")
println(obj)
print("Insert R[ind] to flip row, C[ind] to flip a column, Q to quit: ")
input = match(r"([qrc])(\d+)"i, line)
if input ≢ nothing && all(input.captures .≢ nothing)
dim = Symbol(uppercase(input.captures[1]))
ind = Index{dim}(parse(Int, input.captures[2]))
flipbits!(mat, ind)
nflips += 1
elseif occursin("q", line)
println("\nSEE YOU SOON!")
return
else
println("\nINPUT NOT VALID, RETRY!\n")
end
end
println("\nSUCCED! In ", nflips, " flips.")
println(mat)
return
end

end  # module FlippingBitsGame

using .FlippingBitsGame

FlippingBitsGame.play()

```

{{output}}

```Insert the size of the matrix (nrow [> 1] *space* ncol [> 1]):3 3

0 flips until now.
Current configuration:
1  2  3
---------
1 | F  F  F
2 | T  F  T
3 | F  F  T

Objective configuration:
1  2  3
---------
1 | F  F  T
2 | F  T  T
3 | F  F  F

Insert R[ind] to flip row, C[ind] to flip a column, Q to quit: c3

1 flips until now.
Current configuration:
1  2  3
---------
1 | F  F  T
2 | T  F  F
3 | F  F  F

Objective configuration:
1  2  3
---------
1 | F  F  T
2 | F  T  T
3 | F  F  F

Insert R[ind] to flip row, C[ind] to flip a column, Q to quit: r2

SUCCED! In 2 flips.
1  2  3
---------
1 | F  F  T
2 | F  T  T
3 | F  F  F

```

## Kotlin

```// version 1.1.3

import java.util.Random

val rand = Random()
val target = Array(3) { IntArray(3) { rand.nextInt(2) } }
val board  = Array(3) { IntArray(3) }

fun flipRow(r: Int) {
for (c in 0..2) board[r][c] = if (board[r][c] == 0) 1 else 0
}

fun flipCol(c: Int) {
for (r in 0..2) board[r][c] = if (board[r][c] == 0) 1 else 0
}

/** starting from the target we make 9 random row or column flips */
fun initBoard() {
for (i in 0..2) {
for (j in 0..2) board[i][j] = target[i][j]
}
repeat(9) {
val rc = rand.nextInt(2)
if (rc == 0)
flipRow(rand.nextInt(3))
else
flipCol(rand.nextInt(3))
}
}

fun printBoard(label: String, isTarget: Boolean = false) {
val a = if (isTarget) target else board
println("\$label:")
println("  | a b c")
println("---------")
for (r in 0..2) {
print("\${r + 1} |")
for (c in 0..2) print(" \${a[r][c]}")
println()
}
println()
}

fun gameOver(): Boolean {
for (r in 0..2) {
for (c in 0..2) if (board[r][c] != target[r][c]) return false
}
return true
}

fun main(args: Array<String>) {
// initialize board and ensure it differs from the target i.e. game not already over!
do {
initBoard()
}
while(gameOver())

printBoard("TARGET", true)
printBoard("OPENING BOARD")
var flips = 0

do {
var isRow = true
var n = -1
do {
print("Enter row number or column letter to be flipped: ")
val ch = if (input.isNotEmpty()) input[0].toLowerCase() else '0'
if (ch !in "123abc") {
println("Must be 1, 2, 3, a, b or c")
continue
}
if (ch in '1'..'3') {
n = ch.toInt() - 49
}
else {
isRow = false
n = ch.toInt() - 97
}
}
while (n == -1)

flips++
if (isRow) flipRow(n) else flipCol(n)
val plural = if (flips == 1) "" else "S"
printBoard("\nBOARD AFTER \$flips FLIP\$plural")
}
while (!gameOver())

val plural = if (flips == 1) "" else "s"
println("You've succeeded in \$flips flip\$plural")
}
```

{{out}} A sample game:

```
TARGET:
| a b c
---------
1 | 0 1 0
2 | 0 1 0
3 | 1 1 1

OPENING BOARD:
| a b c
---------
1 | 1 0 0
2 | 0 1 1
3 | 0 0 1

Enter row number or column letter to be flipped: 1

BOARD AFTER 1 FLIP:
| a b c
---------
1 | 0 1 1
2 | 0 1 1
3 | 0 0 1

Enter row number or column letter to be flipped: 3

BOARD AFTER 2 FLIPS:
| a b c
---------
1 | 0 1 1
2 | 0 1 1
3 | 1 1 0

Enter row number or column letter to be flipped: c

BOARD AFTER 3 FLIPS:
| a b c
---------
1 | 0 1 0
2 | 0 1 0
3 | 1 1 1

You've succeeded in 3 flips!

```

## Lua

```
target, board, moves, W, H = {}, {}, 0, 3, 3

function getIndex( i, j ) return i + j * W - W end

function flip( d, r )
function invert( a ) if a == 1 then return 0 end return 1 end
local idx
if d == 1 then
for i = 1, W do
idx = getIndex( i, r )
board[idx] = invert( board[idx] )
end
else
for i = 1, H do
idx = getIndex( r, i )
board[idx] = invert( board[idx] )
end
end
moves = moves + 1
end
function createTarget()
target, board = {}, {}
local idx
for j = 1, H do
for i = 1, W do
idx = getIndex( i, j )
if math.random() < .5 then target[idx] = 0
else target[idx] = 1
end
board[idx] = target[idx]
end
end
for i = 1, 103 do
if math.random() < .5 then flip( 1, math.random( H ) )
else flip( 2, math.random( W ) )
end
end
moves = 0
end
function getUserInput()
io.write( "Input row and/or column: " ); local r = io.read()
local a
for i = 1, #r do
a = string.byte( r:sub( i, i ):lower() )
if a >= 48 and a <= 57 then flip( 2, a - 48 ) end
if a >= 97 and a <= string.byte( 'z' ) then flip( 1, a - 96 ) end
end
end
function solved()
local idx
for j = 1, H do
for i = 1, W do
idx = getIndex( i, j )
if target[idx] ~= board[idx] then return false end
end
end
return true
end
function display()
local idx
io.write( "\nTARGET\n   " )
for i = 1, W do io.write( string.format( "%d  ", i ) ) end; print()
for j = 1, H do
io.write( string.format( "%s  ", string.char( 96 + j ) ) )
for i = 1, W do
idx = getIndex( i, j )
io.write( string.format( "%d  ", target[idx] ) )
end; io.write( "\n" )
end
io.write( "\nBOARD\n   " )
for i = 1, W do io.write( string.format( "%d  ", i ) ) end; print()
for j = 1, H do
io.write( string.format( "%s  ", string.char( 96 + j ) ) )
for i = 1, W do
idx = getIndex( i, j )
io.write( string.format( "%d  ", board[idx] ) )
end; io.write( "\n" )
end
io.write( string.format( "Moves: %d\n", moves ) )
end
function play()
while true do
createTarget()
repeat
display()
getUserInput()
until solved()
display()
io.write( "Very well!\nPlay again(Y/N)? " );
if io.read():lower() ~= "y" then return end
end
end
--[[entry point]]--
math.randomseed( os.time() )
play()

```

{{out}}

```
TARGET
1  2  3
a  0  0  0
b  0  0  0
c  1  0  0

BOARD
1  2  3
a  1  1  0
b  0  0  1
c  0  1  0
Moves: 0
Input row and/or column: 3ac

TARGET
1  2  3
a  0  0  0
b  0  0  0
c  1  0  0

BOARD
1  2  3
a  0  0  0
b  0  0  0
c  1  0  0
Moves: 3
Very well!
Play again(Y/N)?

```

## Maple

Click [http://maplecloud.maplesoft.com/application.jsp?appId=5721146878066688 here] to play this game online.

```FlippingBits := module()
export ModuleApply;
local gameSetup, flip, printGrid, checkInput;
local board;

gameSetup := proc(n)
local r, c, i, toFlip, target;
randomize():
target := Array( 1..n, 1..n, rand(0..1) );
board := copy(target);
for i to rand(3..9)() do
toFlip := [0, 0];
toFlip[1] := StringTools[Random](1, "rc");
toFlip[2] := convert(rand(1..n)(), string);
flip(toFlip);
end do;
return target;
end proc;

flip := proc(line)
local i, lineNum;
lineNum := parse(op(line[2..-1]));
for i to upperbound(board)[1] do
if line[1] = "R" then
board[lineNum, i] := `if`(board[lineNum, i] = 0, 1, 0);
else
board[i, lineNum] := `if`(board[i, lineNum] = 0, 1, 0);
end if;
end do;
return NULL;
end proc;

printGrid := proc(grid)
local r, c;
for r to upperbound(board)[1] do
for c to upperbound(board)[1] do
printf("%a ", grid[r, c]);
end do;
printf("\n");
end do;
printf("\n");
return NULL;
end proc;

checkInput := proc(input)
try
if input[1] = "" then
return false, "";
elif not input[1] = "R" and not input[1] = "C" then
elif not type(parse(op(input[2..-1])), posint) then
error;
elif parse(op(input[2..-1])) < 1 or parse(op(input[2..-1])) > upperbound(board)[1] then
return false, "Row or column number too large or too small.";
end if;
catch:
return false, "Please indicate a row or column number."
end try;
return true, "";
end proc;

ModuleApply := proc(n)
local gameOver, toFlip, target, answer, restart;
restart := true;
while restart do
target := gameSetup(n);
while ArrayTools[IsEqual](target, board) do
target := gameSetup(n);
end do;
gameOver := false;
while not gameOver do
printf("The Target:\n");
printGrid(target);
printf("The Board:\n");
printGrid(board);
if ArrayTools[IsEqual](target, board) then
printf("You win!! Press enter to play again or type END to quit.\n\n");
gameOver := true;
restart := false
end if;
else
toFlip := ["", ""];
while not checkInput(toFlip)[1]  and not gameOver do
ifelse (not op(checkInput(toFlip)[2..-1]) = "", printf("%s\n\n", op(checkInput(toFlip)[2..-1])), NULL);
printf("Please enter a row or column to flip. (ex: r1 or c2) Press enter for a new game or type END to quit.\n\n");
gameOver := true;
restart := false;
end if;
end if;
end do;
if not gameOver then
flip(toFlip);
end if;
end if;
end do;
end do;
printf("Game Over!\n");
end proc;
end module:

FlippingBits(3);
```

{{out}}

```
The Target:
1 1 1
1 1 1
1 0 1

The Board:
0 1 1
0 1 1
0 0 1

Please enter a row or column to flip. (ex: r1 or c2) Press enter for a new game or type END to quit.

The Target:
1 1 1
1 1 1
1 0 1

The Board:
1 1 1
1 1 1
1 0 1

You win!! Press enter to play again or type END to quit.

```

## MATLAB

Size can be passed in as an argument or entered after a prompt.

```function FlippingBitsGame(n)
% Play the flipping bits game on an n x n array

% Generate random target array
fprintf('Welcome to the Flipping Bits Game!\n')
if nargin < 1
n = input('What dimension array should we use? ');
end
Tar = logical(randi([0 1], n));

% Generate starting array by randomly flipping rows or columns
Cur = Tar;
while all(Cur(:) == Tar(:))
nFlips = randi([3*n max(10*n, 100)]);
randDim = randi([0 1], nFlips, 1);
randIdx = randi([1 n], nFlips, 1);
for k = 1:nFlips
if randDim(k)
Cur(randIdx(k), :) = ~Cur(randIdx(k), :);
else
Cur(:, randIdx(k)) = ~Cur(:, randIdx(k));
end
end
end

% Print rules
fprintf('Given a %d x %d logical array,\n', n, n)
fprintf('and a target array configuration,\n')
fprintf('attempt to transform the array to the target\n')
fprintf('by inverting the bits in a whole row or column\n')
fprintf('at once in as few moves as possible.\n')
fprintf('Enter the corresponding letter to invert a column,\n')
fprintf('or the corresponding number to invert a row.\n')
fprintf('0 will reprint the target array, and no entry quits.\n\n')
fprintf('Target:\n')
PrintArray(Tar)

% Play until player wins or quits
move = true;
nMoves = 0;
while ~isempty(move) && any(Cur(:) ~= Tar(:))
fprintf('Move %d:\n', nMoves)
PrintArray(Cur)
move = lower(input('Enter move: ', 's'));
if length(move) > 1
fprintf('Invalid move, try again\n')
elseif move
r = str2double(move);
if isnan(r)
c = move-96;
if c > n || c < 1
fprintf('Invalid move, try again\n')
else
Cur(:, c) = ~Cur(:, c);
nMoves = nMoves+1;
end
else
if r > n || r < 0
fprintf('Invalid move, try again\n')
elseif r == 0
fprintf('Target:\n')
PrintArray(Tar)
else
Cur(r, :) = ~Cur(r, :);
nMoves = nMoves+1;
end
end
end
end

if all(Cur(:) == Tar(:))
fprintf('You win in %d moves! Try not to flip out!\n', nMoves)
else
fprintf('Quitting? The challenge a bit much for you?\n')
end
end

function PrintArray(A)
[nRows, nCols] = size(A);
fprintf('        ')
fprintf(' %c', (1:nCols)+96)
fprintf('\n')
for r = 1:nRows
fprintf('%8d%s\n', r, sprintf(' %d', A(r, :)))
end
fprintf('\n')
end
```

{{out}} Normal play and winning:

```Welcome to the Flipping Bits Game!
What dimension array should we use? 3
Given a 3 x 3 logical array,
and a target array configuration,
attempt to transform the array to the target
by inverting the bits in a whole row or column
at once in as few moves as possible.
Enter the corresponding letter to invert a column,
or the corresponding number to invert a row.
0 will reprint the target array, and no entry quits.

Target:
a b c
1 0 0 0
2 0 1 0
3 0 0 0

Move 0:
a b c
1 1 1 1
2 1 0 1
3 1 1 1

Enter move: a
Move 1:
a b c
1 0 1 1
2 0 0 1
3 0 1 1

Enter move: b
Move 2:
a b c
1 0 0 1
2 0 1 1
3 0 0 1

Enter move: c
You win in 3 moves! Try not to flip out!
```

Bad input, reprinting target, and quitting:

```Welcome to the Flipping Bits Game!
What dimension array should we use? 3
Given a 3 x 3 logical array,
and a target array configuration,
attempt to transform the array to the target
by inverting the bits in a whole row or column
at once in as few moves as possible.
Enter the corresponding letter to invert a column,
or the corresponding number to invert a row.
0 will reprint the target array, and no entry quits.

Target:
a b c
1 0 0 1
2 1 0 0
3 1 0 0

Move 0:
a b c
1 0 0 0
2 0 1 0
3 0 1 0

Enter move: a
Move 1:
a b c
1 1 0 0
2 1 1 0
3 1 1 0

Enter move: b
Move 2:
a b c
1 1 1 0
2 1 0 0
3 1 0 0

Enter move: 0
Target:
a b c
1 0 0 1
2 1 0 0
3 1 0 0

Move 2:
a b c
1 1 1 0
2 1 0 0
3 1 0 0

Enter move: hello
Invalid move, try again
Move 2:
a b c
1 1 1 0
2 1 0 0
3 1 0 0

Enter move: d
Invalid move, try again
Move 2:
a b c
1 1 1 0
2 1 0 0
3 1 0 0

Enter move: 4
Invalid move, try again
Move 2:
a b c
1 1 1 0
2 1 0 0
3 1 0 0

Enter move:
Quitting? The challenge a bit much for you?
```

## MiniScript

```// Flipping Bits game.
// Transform a start grid to an end grid by flipping rows or columns.

size = 3

board = []
goal = []
for i in range(1,size)
row = []
for j in range(1,size)
row.push (rnd > 0.5)
end for
board.push row
goal.push row[0:]
end for

flipRow = function(n)
for j in range(0, size-1)
board[n-1][j] = not board[n-1][j]
end for
end function

flipCol = function(n)
for i in range(0, size-1)
board[i][n-1] = not board[i][n-1]
end for
end function

flipAny = function(s)
s = s[0].upper
if s >= "A" then flipCol s.code - 64 else flipRow val(s)
end function

for scramble in range(20)
if rnd < 0.5 then flipRow ceil(rnd*size) else flipCol ceil(rnd*size)
end for

solved = function()
for i in range(0, size-1)
for j in range(0, size-1)
if board[i][j] != goal[i][j] then return false
end for
end for
return true
end function

moveCount = 0
while true
print "  CURRENT:" + " "*(4+size*3) + "GOAL:"
for i in range(1,size)
s = i + " " + str(board[i-1])
s = s + " "*(3+size*3) + str(goal[i-1])
print s
end for
s = "   "
for i in range(1,size)
s = s + char(64+i) + "  "
end for
print s
if solved then break
moveCount = moveCount + 1
inp = input("Move " + moveCount + "? ")
flipAny(inp)
end while
print "You did it!"
```

{{out}}

```  CURRENT:             GOAL:
1 [0, 0, 0]            [0, 1, 1]
2 [1, 0, 1]            [1, 1, 0]
3 [1, 1, 0]            [0, 1, 0]
A  B  C
Move 1? 1
CURRENT:             GOAL:
1 [1, 1, 1]            [0, 1, 1]
2 [1, 0, 1]            [1, 1, 0]
3 [1, 1, 0]            [0, 1, 0]
A  B  C
Move 2? a
CURRENT:             GOAL:
1 [0, 1, 1]            [0, 1, 1]
2 [0, 0, 1]            [1, 1, 0]
3 [0, 1, 0]            [0, 1, 0]
A  B  C
Move 3? 2
CURRENT:             GOAL:
1 [0, 1, 1]            [0, 1, 1]
2 [1, 1, 0]            [1, 1, 0]
3 [0, 1, 0]            [0, 1, 0]
A  B  C
You did it!
```

## OCaml

```module FlipGame =
struct
type t = bool array array

let make side = Array.make_matrix side side false

let flipcol b n =
for i = 0 to (Array.length b - 1) do
b.(n).(i) <- not b.(n).(i)
done

let fliprow b n =
for i = 0 to (Array.length b - 1) do
b.(i).(n) <- not b.(i).(n)
done

let randflip b =
let n = Random.int (Array.length b - 1) in
match Random.bool () with
| true -> fliprow b n
| false -> flipcol b n

let rec game side steps =
let start, target = make side, make side in
for i = 1 to steps do
randflip start;
randflip target
done;
if start = target then game side steps (* try again *) else
(start, target)

let print b =
for i = 0 to Array.length b - 1 do
for j = 0 to Array.length b - 1 do
Printf.printf " %d " (if b.(j).(i) then 1 else 0)
done;
print_newline ()
done;
print_newline ()

let draw_game board target =
print_endline "TARGET"; print target;
print_endline "BOARD"; print board
end

let play () =
let module G = FlipGame in
let board, target = G.game 3 10 in
let steps = ref 0 in
while board <> target do
G.draw_game board target;
print_string "> ";
flush stdout;
incr steps;
match String.split_on_char ' ' (read_line ()) with
| ["row"; row] ->
(match int_of_string_opt row with
| Some n -> G.fliprow board n
| None -> print_endline "(nothing happens)")
| ["col"; col] ->
(match int_of_string_opt col with
| Some n -> G.flipcol board n
| None -> print_endline "(nothing happens)")
| _ -> ()
done;
G.draw_game board target;
Printf.printf "\n\nGame solved in %d steps\n" !steps

let () =
if not !Sys.interactive then
(Random.self_init ();
play ())
```

{{out}}

```\$ ocamlc flipgame.ml -o flipgame
\$ ./flipgame
TARGET
0  0  1
0  0  1
1  1  0

BOARD
0  1  0
1  0  1
0  1  0

> col 1
TARGET
0  0  1
0  0  1
1  1  0

BOARD
0  0  0
1  1  1
0  0  0

> row 2
TARGET
0  0  1
0  0  1
1  1  0

BOARD
0  0  0
1  1  1
1  1  1

> col 2
TARGET
0  0  1
0  0  1
1  1  0

BOARD
0  0  1
1  1  0
1  1  0

> row 1
TARGET
0  0  1
0  0  1
1  1  0

BOARD
0  0  1
0  0  1
1  1  0

Game solved in 4 steps
```

## Perl

Pass the size of the puzzle on the command line. It defaults to 4. You can play any size game between 2 and 26. While playing, the game accepts anything which looks like valid rows or columns, and disregards any irrelevant text in between.

```#!perl
use strict;
use warnings qw(FATAL all);

my \$n = shift(@ARGV) || 4;
if( \$n < 2 or \$n > 26 ) {
die "You can't play a size \$n game\n";
}

my \$n2 = \$n*\$n;

my (@rows, @cols);
for my \$i ( 0 .. \$n-1 ) {
my \$row = my \$col = "\x00" x \$n2;
vec(\$row, \$i * \$n + \$_, 8) ^= 1 for 0 .. \$n-1;
vec(\$col, \$i + \$_ * \$n, 8) ^= 1 for 0 .. \$n-1;
push @rows, \$row;
push @cols, \$col;
}

my \$goal = "0" x \$n2;
int(rand(2)) or (vec(\$goal, \$_, 8) ^= 1) for 0 .. \$n2-1;
my \$start = \$goal;
{
for(@rows, @cols) {
\$start ^= \$_ if int rand 2;
}
redo if \$start eq \$goal;
}

my @letters = ('a'..'z')[0..\$n-1];
sub to_strings {
my \$board = shift;
my @result = join(" ", "  ", @letters);
for( 0 .. \$n-1 ) {
my \$res = sprintf("%2d ",\$_+1);
\$res .= join " ", split //, substr \$board, \$_*\$n, \$n;
push @result, \$res;
}
\@result;
}

my \$fmt;
my (\$stext, \$etext) = ("Starting board", "Ending board");
my \$re = join "|", reverse 1 .. \$n, @letters;
my \$moves_so_far = 0;
while( 1 ) {
my (\$from, \$to) = (to_strings(\$start), to_strings(\$goal));
unless( \$fmt ) {
my \$len = length \$from->[0];
\$len = length(\$stext) if \$len < length \$stext;
\$fmt = join(\$len, "%", "s%", "s\n");
}
printf \$fmt, \$stext, \$etext;
printf \$fmt, \$from->[\$_], \$to->[\$_] for 0 .. \$n;
last if \$start eq \$goal;
INPUT_LOOP: {
printf "Move #%s: Type one or more row numbers and/or column letters: ",
\$moves_so_far+1;
my \$input = <>;
die unless defined \$input;
my \$did_one;
for( \$input =~ /(\$re)/gi ) {
\$did_one = 1;
if( /\d/ ) {
\$start ^= \$rows[\$_-1];
} else {
\$_ = ord(lc) - ord('a');
\$start ^= \$cols[\$_];
}
++\$moves_so_far;
}
redo INPUT_LOOP unless \$did_one;
}
}
print "You won after \$moves_so_far moves.\n";
```

{{out}}

```\$ perl FlippingBitsGame.pl 3
Starting board  Ending board
a b c         a b c
1 0 0 1       1 1 1 1
2 0 1 1       2 1 0 1
3 0 0 0       3 0 0 1
Move #1: Type one or more row numbers and/or column letters: 12
Starting board  Ending board
a b c         a b c
1 1 1 0       1 1 1 1
2 1 0 0       2 1 0 1
3 0 0 0       3 0 0 1
Move #3: Type one or more row numbers and/or column letters: c
Starting board  Ending board
a b c         a b c
1 1 1 1       1 1 1 1
2 1 0 1       2 1 0 1
3 0 0 1       3 0 0 1
You won after 3 moves.
```

The same game could have been won after typing 1 2 c in any order, with multiple lines or even "12c" on a single line.

## Perl 6

{{Works with|rakudo|2016.11}} Pass in a parameter to set the square size for the puzzle. (Defaults to 4.) Arbitrarily limited to between 1 and 26. Yes, you can choose to solve a 1 element square puzzle, but it won't be very challenging. Accepts upper or lower case letters for columns. Disregards any out-of-range indices. Enter a blank or 0 (zero) to exit.

```sub MAIN (\$square = 4) {
say "{\$square}? Seriously?" and exit if \$square < 1 or \$square > 26;
my %bits = map { \$_ => %( map { \$_ => 0 }, ('A' .. *)[^ \$square] ) },
(1 .. *)[^ \$square];
scramble %bits;
my \$target = build %bits;
scramble %bits until build(%bits) ne \$target;
display(\$target, %bits);
my \$turns = 0;
while my \$flip = prompt "Turn {++\$turns}: Flip which row / column? " {
flip \$flip.match(/\w/).uc, %bits;
if display(\$target, %bits) {
say "Hurray! You solved it in \$turns turns.";
last;
}
}
}

sub display(\$goal, %hash) {
shell('clear');
say "Goal\n\$goal\nYou";
my \$this = build %hash;
say \$this;
return (\$goal eq \$this);
}

sub flip (\$a, %hash) {
given \$a {
when any(keys %hash) {
%hash{\$a}{\$_} = %hash{\$a}{\$_} +^ 1 for %hash{\$a}.keys
};
when any(keys %hash{'1'}) {
%hash{\$_}{\$a} = %hash{\$_}{\$a} +^ 1 for %hash.keys
};
}
}

sub build (%hash) {
my \$string = '   ';
\$string ~= sprintf "%2s ", \$_ for sort keys %hash{'1'};
\$string ~= "\n";
for %hash.keys.sort: +* -> \$key {
\$string ~= sprintf "%2s ", \$key;
\$string ~= sprintf "%2s ", %hash{\$key}{\$_} for sort keys %hash{\$key};
\$string ~=  "\n";
};
\$string
}

sub scramble(%hash) {
my @keys = keys %hash;
@keys.push: | keys %hash{'1'};
flip \$_,  %hash for @keys.pick( @keys/2 );
}
```

A sample 3 x 3 game might look like this:

```Goal
A  B  C
1  1  1  0
2  0  0  1
3  1  1  0

You
A  B  C
1  0  0  0
2  1  1  1
3  1  1  1

Turn 1: Flip which row / column? 2

Goal
A  B  C
1  1  1  0
2  0  0  1
3  1  1  0

You
A  B  C
1  0  0  0
2  0  0  0
3  1  1  1

Turn 2: Flip which row / column? 1

Goal
A  B  C
1  1  1  0
2  0  0  1
3  1  1  0

You
A  B  C
1  1  1  1
2  0  0  0
3  1  1  1

Turn 3: Flip which row / column? c

Goal
A  B  C
1  1  1  0
2  0  0  1
3  1  1  0

You
A  B  C
1  1  1  0
2  0  0  1
3  1  1  0

Hurray! You solved it in 3 turns.
```

## Phix

```integer w, h

string board, target

procedure new_board()
board = ""
h = prompt_number("Enter number of rows(1..9):",{1,9})
w = prompt_number("Enter number of columns(1..26):",{1,26})
string line = ""
for j=1 to w do line &= 'A'+j-1 end for
board = "  "&line&"\n"
for i=1 to h do
line = '0'+i&" "
for j=1 to w do line &= '0'+rand(2)-1 end for
board &= line&"\n"
end for
end procedure

procedure show_bt()
sequence sb = split(board,'\n'),
st = split(target,'\n')
printf(1,"board:%s     target:%s\n",{sb[1],st[1]})
for i=2 to length(sb)-1 do
printf(1,"      %s            %s\n",{sb[i],st[i]})
end for
end procedure

procedure flip(integer ch, bool bShow=true)
integer k
if ch>='A' and ch<='A'+w-1 then
-- flip_column
ch = ch-'A'+1
for i=1 to h do
k = 2+ch+i*(w+3)
board[k] = '0'+'1'-board[k]
end for
k = 2+ch
elsif ch>='1' and ch<='0'+h then
-- flip_row
ch -= '0'
for i=1 to w do
k = 2+i+(ch)*(w+3)
board[k] = '0'+'1'-board[k]
end for
k = 1+(ch)*(w+3)
else
?9/0    -- sanity check
end if
if bShow then
integer wasch = board[k]
board[k] = '*'
show_bt()
board[k] = wasch
end if
end procedure

procedure scramble_board()
integer lim = 10000
while 1 do
for i=1 to lim do
if rand(2)=1 then
flip('A'-1+rand(w),false)
else
flip('0'+rand(h),false)
end if
end for
if board!=target then exit end if
lim -= 1 -- sidestep the degenerate 1x1 case
end while
end procedure

function solve_board()
-- not guaranteed optimal (the commented-out length check clogs it on larger boards)
string original = board, moves
sequence next = {{0,board,""}},
legal_moves = tagset('A'+w-1,'A')&tagset('0'+h,'1')
atom t2 = time()+2 -- in case board is illegal/unsolveable
while time()<t2 do
for lm=1 to length(legal_moves) do
integer c = legal_moves[lm]
{?,board,moves} = next[1]
flip(c,false)
moves &= c
if board = target then
board = original
return moves
end if
next = append(next,{sum(sq_eq(board,target)),board,moves})
for i=length(next) to 3 by -1 do
if next[i][1]<=next[i-1][1] then exit end if
--              if length(next[i][3])>length(next[i-1][3]) then exit end if
{next[i-1],next[i]} = {next[i],next[i-1]}
end for
end for
next = next[2..\$]
end while
board = original
return 0
end function

constant ESC = #1B

procedure main()
integer moves = 0, solves = 0, ch
bool took_hint = false
new_board()
target = board
scramble_board()
show_bt()
object soln = solve_board()
while 1 do
string solve = iff(string(soln)?sprintf(" solveable in %d,",length(soln)):"")
printf(1,"moves taken %d,%s enter your move (A..%c or 1..%c) or ?:",{moves,solve,'A'+w-1,'0'+h})
while 1 do
ch = upper(wait_key())
if ch<=#FF then exit end if -- (ignore control keys)
end while
printf(1,"%c\n",ch)
if (ch>='A' and ch<='A'+w-1)
or (ch>='1' and ch<='0'+h) then
flip(ch)
if board=target then
printf(1,"\nWell %s!\n\n",{iff(took_hint?"cheated","done")})
exit
end if
moves += 1
soln = iff(string(soln) and ch=soln[1]?soln[2..\$]:solve_board())
elsif string(soln) and
(ch='H' -- (nb consumed above if w>=8)
or ch='.') then
took_hint = true
printf(1,"hint: %c\n",soln[1])
elsif ch='Q' -- (nb consumed above if w>=17)
or ch=ESC then
exit
elsif string(soln) and
(ch='S' -- (nb consumed above if w>=19)
or ch='!') then
for i=1 to length(soln) do
printf(1,"auto-solving, move %d:\n",i)
flip(soln[i])
sleep(2)
end for
exit
else
puts(1,"press ")
if string(soln) then
puts(1,"'!' (or 's' if width<19) to solve the board automatically,\n")
puts(1,"      '.' (or 'h' if width<8) to show hint,\n")
end if
puts(1,"      escape (or 'q' if width<17) to quit\n")
end if
end while
end procedure
main()
```

{{out}}

```
Enter number of rows(1..9):2
Enter number of columns(1..26):2
board:  AB     target:  AB
1 11            1 10
2 00            2 10
moves taken 0, solveable in 2, enter your move (A..B or 1..2) or ?:?
press '!' (or 's' if width<19) to solve the board automatically,
'.' (or 'h' if width<8) to show hint,
escape (or 'q' if width<17) to quit
moves taken 0, solveable in 2, enter your move (A..B or 1..2) or ?:H
hint: A
moves taken 0, solveable in 2, enter your move (A..B or 1..2) or ?:A
board:  *B     target:  AB
1 01            1 10
2 10            2 10
moves taken 1, solveable in 1, enter your move (A..B or 1..2) or ?:H
hint: 1
moves taken 1, solveable in 1, enter your move (A..B or 1..2) or ?:1
board:  AB     target:  AB
* 10            1 10
2 10            2 10

Well cheated!

```

An auto solve:

```
Enter number of rows(1..9):2
Enter number of columns(1..26):2
board:  AB     target:  AB
1 10            1 00
2 10            2 11
moves taken 0, solveable in 2, enter your move (A..B or 1..2) or ?:!
auto-solving, move 1:
board:  *B     target:  AB
1 00            1 00
2 00            2 11
auto-solving, move 2:
board:  AB     target:  AB
1 00            1 00
* 11            2 11

```

The maximum board size is 9x26:

```
Enter number of rows(1..9):9
Enter number of columns(1..26):26
board:  ABCDEFGHIJKLMNOPQRSTUVWXYZ     target:  ABCDEFGHIJKLMNOPQRSTUVWXYZ
1 11010000101000110010101101            1 00010011000001110010101001
2 10000011010000110100001100            2 10111111000110001011110111
3 00100011010011100110111101            3 11100000111010100110111001
4 00101110001111100001001000            4 00010010011001011110110011
5 01001001111011101011100011            5 10001010010010101011100111
6 01010001101111101110111011            6 10010010000110101110111111
7 10011000011101100100000111            7 01011011110100100100000011
8 01111100111110000001100101            8 01000000101000111110011110
9 00111000101100111000011011            9 11111011000101111000011111
moves taken 0, solveable in 11, enter your move (A..Z or 1..9) or ?:

```

And the minimum is 1x1:

```
Enter number of rows(1..9):1
Enter number of columns(1..26):1
board:  A     target:  A
1 0            1 1
moves taken 0, solveable in 1, enter your move (A..A or 1..1) or ?:1
board:  A     target:  A
* 1            1 1
Well done!

```

## PL/I

```(subscriptrange, stringrange, stringsize):
flip: procedure options (main);
declare n fixed binary;

put skip list ('This is the bit-flipping game.  What size of board do you want?');
get list (n);
put skip list
('Your task is to change your board so as match the board on the right (the objective)');

begin;
declare initial(n,n) bit (1), objective(n,n) bit (1);
declare (i, j, k, move) fixed binary;
declare ch character(1);
declare alphabet character (26) initial ('abcdefghijklmnopqrstuvwxyz');

on subrg
begin; put skip list ('Your row or column ' || trim(ch) || ' is out of range'); stop; end;

initial, objective = iand(random()*99, 1) = 1;

/* Set up the objective array: */
do i = 1 to n-1;
j = random()*n+1;  objective(j,*) = ^objective(j,*);
j = random()*n+1;  objective(*,j) = ^objective(*,j);
end;

do move = 0 by 1;
put skip edit ( center('You', n*3), center('The objective', 3*n+4) ) (x(3), a);
put skip edit ( (substr(alphabet, i, 1) do i = 1 to n) ) (x(5), (n) a(3));
put      edit ( (substr(alphabet, i, 1) do i = 1 to n) ) (x(3), (n) a(3));
do i = 1 to n;
put skip edit (i, initial(i,*), objective(i,*)) ((n+1) f(3), x(3), (n) F(3));
end;

if all(initial = objective) then leave;

put skip(2) list
('Please type a row number or column letter whose bits you want to flip: ');
get edit (ch) (L); put edit (ch) (a);
k = index(alphabet, ch);
if k > 0 then
initial(*, k) = ^initial(*,k); /* Flip column k */
else
initial(ch,*) = ^initial(ch,*); /* Flip row ch */
end;
put skip(2) list ('Congratulations. You solved it in ' || trim(move) || ' moves.');
end;

end flip;
```

{{out}}

```
This is the bit-flipping game.  What size of board do you want?

Your task is to change your board so as match the board on the right (the objective)
You      The objective
a  b  c     a  b  c
1  1  1  1     0  1  1
2  0  0  0     1  0  0
3  1  1  1     1  0  0

Please type a row number or column letter whose bits you want to flip:
3
You      The objective
a  b  c     a  b  c
1  1  1  1     0  1  1
2  0  0  0     1  0  0
3  0  0  0     1  0  0

Please type a row number or column letter whose bits you want to flip:
a
You      The objective
a  b  c     a  b  c
1  0  1  1     0  1  1
2  1  0  0     1  0  0
3  1  0  0     1  0  0

Congratulations. You solved it in 2 moves.

```

## Python

```"""
Given a %i by %i sqare array of zeroes or ones in an initial
configuration, and a target configuration of zeroes and ones
The task is to transform one to the other in as few moves as
possible by inverting whole numbered rows or whole lettered
columns at once.
In an inversion any 1 becomes 0 and any 0 becomes 1 for that
whole row or column.

"""

from random import randrange
from copy import deepcopy
from string import ascii_lowercase

try:    # 2to3 fix
input = raw_input
except:
pass

N = 3   # N x N Square arrray

board  = [[0]* N for i in range(N)]

def setbits(board, count=1):
for i in range(count):
board[randrange(N)][randrange(N)] ^= 1

def shuffle(board, count=1):
for i in range(count):
if randrange(0, 2):
fliprow(randrange(N))
else:
flipcol(randrange(N))

def pr(board, comment=''):
print(str(comment))
print('     ' + ' '.join(ascii_lowercase[i] for i in range(N)))
print('  ' + '\n  '.join(' '.join(['%2s' % j] + [str(i) for i in line])
for j, line in enumerate(board, 1)))

def init(board):
setbits(board, count=randrange(N)+1)
target = deepcopy(board)
while board == target:
shuffle(board, count=2 * N)
prompt = '  X, T, or 1-%i / %s-%s to flip: ' % (N, ascii_lowercase[0],
ascii_lowercase[N-1])
return target, prompt

def fliprow(i):
board[i-1][:] = [x ^ 1 for x in board[i-1] ]

def flipcol(i):
for row in board:
row[i] ^= 1

if __name__ == '__main__':
print(__doc__ % (N, N))
target, prompt = init(board)
pr(target, 'Target configuration is:')
print('')
turns = 0
while board != target:
turns += 1
pr(board, '%i:' % turns)
ans = input(prompt).strip()
if (len(ans) == 1
and ans in ascii_lowercase and ascii_lowercase.index(ans) < N):
flipcol(ascii_lowercase.index(ans))
elif ans and all(ch in '0123456789' for ch in ans) and 1 <= int(ans) <= N:
fliprow(int(ans))
elif ans == 'T':
pr(target, 'Target configuration is:')
turns -= 1
elif ans == 'X':
break
else:
print("  I don't understand %r... Try again. "
"(X to exit or T to show target)\n" % ans[:9])
turns -= 1
else:
print('\nWell done!\nBye.')
```

{{out}}

```Given a 3 by 3 sqare array of zeroes or ones in an initial
configuration, and a target configuration of zeroes and ones
The task is to transform one to the other in as few moves as
possible by inverting whole numbered rows or whole lettered
columns at once.
In an inversion any 1 becomes 0 and any 0 becomes 1 for that
whole row or column.

Target configuration is:
a b c
1 0 1 0
2 0 0 0
3 0 0 0

1:
a b c
1 1 0 0
2 0 0 1
3 0 0 1
X, T, or 1-3 / a-c to flip: 1
2:
a b c
1 0 1 1
2 0 0 1
3 0 0 1
X, T, or 1-3 / a-c to flip: c

Well done!
Bye.
```

```Target configuration is:
a b c
1 0 0 0
2 0 0 0
3 0 0 1

1:
a b c
1 1 0 1
2 0 1 0
3 0 1 1
X, T, or 1-3 / a-c to flip: 3
2:
a b c
1 1 0 1
2 0 1 0
3 1 0 0
X, T, or 1-3 / a-c to flip: 4
I don't understand '4'... Try again. (X to exit or T to show target)

2:
a b c
1 1 0 1
2 0 1 0
3 1 0 0
X, T, or 1-3 / a-c to flip: c
3:
a b c
1 1 0 0
2 0 1 1
3 1 0 1
X, T, or 1-3 / a-c to flip: d
I don't understand 'd'... Try again. (X to exit or T to show target)

3:
a b c
1 1 0 0
2 0 1 1
3 1 0 1
X, T, or 1-3 / a-c to flip: T
Target configuration is:
a b c
1 0 0 0
2 0 0 0
3 0 0 1
3:
a b c
1 1 0 0
2 0 1 1
3 1 0 1
X, T, or 1-3 / a-c to flip: X
```

## QB64

RANDOMIZE TIMER DIM SHARED cellsPerSide, legalMoves\$, startB\$, currentB\$, targetB\$, moveCount

restart DO displayStatus IF currentB\$ = targetB\$ THEN 'game done! PRINT " Congratulations, done in"; moveCount; " moves." PRINT "": PRINT " Press y for yes, if you want to start over > "; yes\$ = getKey\$: PRINT yes\$: _DELAY .4: vcls IF yes\$ = "y" THEN restart ELSE nomore = -1 ELSE 'get next move m\$ = " ": PRINT WHILE INSTR(legalMoves\$, m\$) = 0 PRINT " Press a lettered column or a numbered row to flip (or 0,q,?,!) > "; m\$ = getKey\$: PRINT m\$: _DELAY .4 IF m\$ = "!" THEN showSolution = -1: m\$ = " ": EXIT WHILE ELSEIF m\$ = "?" THEN: m\$ = " ": cp CSRLIN, "Hint: " + hint\$ ELSEIF m\$ = "0" OR m\$ = "q" THEN: vcls: CLOSE: END ELSEIF m\$ = "" THEN: m\$ = " " END IF WEND IF showSolution THEN 'run the solution from hints function showSolution = 0: mv\$ = hint\$ cp CSRLIN + 1, "For the next move, the AI has chosen: " + mv\$ cp CSRLIN + 1, "Running the solution with 4 sec screen delays..." _DELAY 4: vcls WHILE mv\$ <> "Done?" moveCount = moveCount + 1: makeMove mv\$: displayStatus: mv\$ = hint\$ cp CSRLIN + 1, "For the next move, the AI has chosen: " + mv\$ cp CSRLIN + 1, "Running the solution with 4 sec screen delays..." _DELAY 4: vcls WEND displayStatus cp CSRLIN + 1, "Done! Current board matches Target" cp CSRLIN + 1, "Press y for yes, if you want to start over: > " yes\$ = getKey\$: PRINT yes\$: _DELAY .4: vcls IF yes\$ = "y" THEN restart ELSE nomore = -1 ELSE vcls: moveCount = moveCount + 1: makeMove m\$ END IF END IF LOOP UNTIL nomore CLOSE

SUB displayStatus COLOR 9: showBoard 2, 2, currentB\$, "Current:" COLOR 12: showBoard 2, 2 + 2 * cellsPerSide + 6, targetB\$, "Target:" COLOR 13: PRINT: PRINT " Number of moves taken so far is" + STR\$(moveCount) COLOR 14 END SUB

FUNCTION hint\$ 'compare the currentB to targetB and suggest letter or digit or done FOR i = 1 TO 2 * cellsPerSide 'check cols first then rows as listed in legalMoves\$ r\$ = MID\$(legalMoves\$, i, 1) IF i <= cellsPerSide THEN currentbit\$ = MID\$(currentB\$, i, 1): targetBit\$ = MID\$(targetB\$, i, 1) IF currentbit\$ <> targetBit\$ THEN flag = -1: EXIT FOR ELSE j = i - cellsPerSide currentbit\$ = MID\$(currentB\$, (j - 1) * cellsPerSide + 1, 1) targetBit\$ = MID\$(targetB\$, (j - 1) * cellsPerSide + 1, 1) IF currentbit\$ <> targetBit\$ THEN flag = -1: EXIT FOR END IF NEXT IF flag THEN hint\$ = r\$ ELSE hint\$ = "Done?" END FUNCTION

SUB restart CLOSE OPEN "Copy Flipping Bits Game.txt" FOR OUTPUT AS #3 cellsPerSide = 0: legalMoves\$ = "": moveCount = 0 COLOR 9: cp 3, "Flipping Bits Game, now with AI! b+ 2017-12-18" COLOR 5 cp 5, "You will be presented with a square board marked Current and" cp 6, "another marked Target. The object of the game is to match" cp 7, "the Current board to Target in the least amount of moves." cp 9, "To make a move, enter a letter for a column to flip or" cp 10, "a digit for a row to flip. In a flip, all 1's are" cp 11, "changed to 0's and all 0's changed to 1's." cp 13, "You may enter 0 or q at any time to quit." cp 14, "You may press ? when prompted for move to get a hint." cp 15, "You may press ! to have the program solve the puzzle." COLOR 14: PRINT: PRINT WHILE cellsPerSide < 2 OR cellsPerSide > 9 LOCATE CSRLIN, 13: PRINT "Please press how many cells you want per side 2 to 9 > "; in\$ = getKey\$: PRINT in\$: _DELAY .4 IF in\$ = "0" OR in\$ = "q" THEN END ELSE cellsPerSide = VAL(in\$) WEND vcls FOR i = 1 TO cellsPerSide: legalMoves\$ = legalMoves\$ + CHR\$(96 + i): NEXT FOR i = 1 TO cellsPerSide: legalMoves\$ = legalMoves\$ + LTRIM\$(STR\$(i)): NEXT startB\$ = startBoard\$: currentB\$ = startB\$: targetB\$ = makeTarget\$: currentB\$ = startB\$ END SUB

FUNCTION startBoard\$ FOR i = 1 TO cellsPerSide ^ 2: r\$ = r\$ + LTRIM\$(STR\$(INT(RND * 2))): NEXT startBoard\$ = r\$ END FUNCTION

SUB showBoard (row, col, board\$, title\$) LOCATE row - 1, col: PRINT title\$ FOR i = 1 TO cellsPerSide LOCATE row, col + 2 * (i - 1) + 3: PRINT MID\$(legalMoves\$, i, 1); NEXT PRINT FOR i = 1 TO cellsPerSide LOCATE row + i, col - 1: PRINT STR\$(i); FOR j = 1 TO cellsPerSide LOCATE row + i, col + 2 * j: PRINT " " + MID\$(board\$, (i - 1) * cellsPerSide + j, 1); NEXT PRINT NEXT END SUB

SUB makeMove (move\$) ac = ASC(move\$) IF ac > 96 THEN 'letter col = ac - 96 FOR i = 1 TO cellsPerSide bit\$ = MID\$(currentB\$, (i - 1) * cellsPerSide + col, 1) IF bit\$ = "0" THEN MID\$(currentB\$, (i - 1) * cellsPerSide + col, 1) = "1" ELSE MID\$(currentB\$, (i - 1) * cellsPerSide + col, 1) = "0" END IF NEXT ELSE 'number row = ac - 48 FOR i = 1 TO cellsPerSide bit\$ = MID\$(currentB\$, (row - 1) * cellsPerSide + i, 1) IF bit\$ = "0" THEN MID\$(currentB\$, (row - 1) * cellsPerSide + i, 1) = "1" ELSE MID\$(currentB\$, (row - 1) * cellsPerSide + i, 1) = "0" END IF NEXT END IF END SUB

FUNCTION makeTarget\$ WHILE currentB\$ = startB\$ FOR i = 1 TO cellsPerSide * cellsPerSide m\$ = MID\$(legalMoves\$, INT(RND * LEN(legalMoves\$)) + 1, 1): makeMove m\$ NEXT WEND makeTarget\$ = currentB\$ END FUNCTION

SUB cp (row, text\$) 'center print at row LOCATE row, (80 - LEN(text\$)) / 2: PRINT text\$; END SUB

SUB vcls 'print the screen to file then clear it DIM s\$(23) FOR lines = 1 TO 23 FOR t = 1 TO 80: scan\$ = scan\$ + CHR\$(SCREEN(lines, t)): NEXT s\$(lines) = RTRIM\$(scan\$): scan\$ = "" NEXT FOR fini = 23 TO 1 STEP -1 IF s\$(fini) <> "" THEN EXIT FOR NEXT PRINT #3, "" FOR i = 1 TO fini: PRINT #3, s\$(i): NEXT PRINT #3, "": PRINT #3, STRING\$(80, "-"): CLS END SUB

FUNCTION getKey\$ 'just want printable characters k\$ = "" WHILE LEN(k\$) = 0 k\$ = INKEY\$ IF LEN(k\$) THEN 'press something so respond IF LEN(k\$) = 2 OR ASC(k\$) > 126 OR ASC(k\$) < 32 THEN k\$ = "*": BEEP END IF WEND getKey\$ = k\$ END FUNCTION

```
'''Output:'''
<lang>
Flipping Bits Game, now with AI!  b+ 2017-12-18

You will be presented with a square board marked Current and
another marked Target. The object of the game is to match
the Current board to Target in the least amount of moves.

To make a move, enter a letter for a column to flip or
a digit for a row to flip. In a flip, all 1's are
changed to 0's and all 0's changed to 1's.

You may enter 0 or q at any time to quit.
You may press ? when prompted for move to get a hint.
You may press ! to have the program solve the puzzle.

Please press how many cells you want per side 2 to 9 > l
Please press how many cells you want per side 2 to 9 > *
Please press how many cells you want per side 2 to 9 > 3

--------------------------------------------------------------------------------

Current:    Target:
a b c       a b c
1  1 1 0    1  0 1 1
2  1 1 0    2  0 1 1
3  0 0 1    3  0 1 1

Number of moves taken so far is 0

Press a lettered column or a numbered row to flip (or 0,q,?,!) > l
Press a lettered column or a numbered row to flip (or 0,q,?,!) > 9
Press a lettered column or a numbered row to flip (or 0,q,?,!) > *
Press a lettered column or a numbered row to flip (or 0,q,?,!) > a

--------------------------------------------------------------------------------

Current:    Target:
a b c       a b c
1  0 1 0    1  0 1 1
2  0 1 0    2  0 1 1
3  1 0 1    3  0 1 1

Number of moves taken so far is 1

Press a lettered column or a numbered row to flip (or 0,q,?,!) > ?
Hint: c
Press a lettered column or a numbered row to flip (or 0,q,?,!) > c

--------------------------------------------------------------------------------

Current:    Target:
a b c       a b c
1  0 1 1    1  0 1 1
2  0 1 1    2  0 1 1
3  1 0 0    3  0 1 1

Number of moves taken so far is 2

Press a lettered column or a numbered row to flip (or 0,q,?,!) > l
Press a lettered column or a numbered row to flip (or 0,q,?,!) > 9
Press a lettered column or a numbered row to flip (or 0,q,?,!) > !

For the next move, the AI has chosen: 3
Running the solution with 4 sec screen delays...

--------------------------------------------------------------------------------

Current:    Target:
a b c       a b c
1  0 1 1    1  0 1 1
2  0 1 1    2  0 1 1
3  0 1 1    3  0 1 1

Number of moves taken so far is 3

For the next move, the AI has chosen: Done?
Running the solution with 4 sec screen delays...

--------------------------------------------------------------------------------

Current:    Target:
a b c       a b c
1  0 1 1    1  0 1 1
2  0 1 1    2  0 1 1
3  0 1 1    3  0 1 1

Number of moves taken so far is 3

Done! Current board matches Target
Press y for yes, if you want to start over: > m

--------------------------------------------------------------------------------

```

## Racket

#lang racket (define (flip-row! pzzl r) (define N (integer-sqrt (bytes-length pzzl))) (for* ((c (in-range N))) (define idx (+ c (* N r))) (bytes-set! pzzl idx (- 1 (bytes-ref pzzl idx)))))

(define (flip-col! pzzl c) (define N (integer-sqrt (bytes-length pzzl))) (for* ((r (in-range N))) (define idx (+ c (* N r))) (bytes-set! pzzl idx (- 1 (bytes-ref pzzl idx)))))

(define (new-game N (flips 10)) (define N2 (sqr N)) (define targ (list->bytes (for/list ((_ N2)) (random 2)))) (define strt (bytes-copy targ)) (for ((_ flips)) (case (random 2) ((0) (flip-col! strt (random N))) ((1) (flip-row! strt (random N))))) (if (equal? strt targ) (new-game N) (values targ strt)))

(define (show-games #:sep (pzl-sep " | ") . pzzls) (define N (integer-sqrt (bytes-length (first pzzls)))) (define caption (string-join (for/list ((c (in-range N))) (~a (add1 c))) "")) (define ruler (string-join (for/list ((c (in-range N))) "-") ""))

(define ((pzzle-row r) p) (string-join (for/list ((c (in-range N))) (~a (bytes-ref p (+ c (* N r))))) ""))

(displayln (string-join (list* (format " ~a" (string-join (for/list ((_ pzzls)) caption) pzl-sep)) (format " ~a" (string-join (for/list ((_ pzzls)) ruler) pzl-sep)) (for/list ((r (in-range N)) (R (in-naturals (char->integer #\a)))) (format "~a ~a" (integer->char R) (string-join (map (pzzle-row r) pzzls) pzl-sep)))) "\n")))

(define (play N) (define-values (end start) (new-game N)) (define (turn n (show? #t)) (cond [(equal? end start) (printf "you won on turn #~a~%" n)] [else (when show? ;; don't show after whitespace (printf "turn #~a~%" n)
(show-games start end)) (match (read-char) [(? eof-object?) (printf "sad to see you go :-(~%")] [(? char-whitespace?) (turn n #f)] [(? char-numeric? c) (define cnum (- (char->integer c) (char->integer #\1))) (cond [(< -1 cnum N) (printf "flipping col ~a~%" (add1 cnum)) (flip-col! start cnum) (turn (add1 n))] [else (printf "column number out of range ~a > ~a~%" (add1 cnum) N) (turn n)])] [(? char-lower-case? c) (define rnum (- (char->integer c) (char->integer #\a))) (cond [(< -1 rnum N) (printf "flipping row ~a~%" (add1 rnum)) (flip-row! start rnum) (turn (add1 n))] [else (printf "row number out of range ~a > ~a~%" (add1 rnum) (sub1 N)) (turn n)])] [else (printf "unrecognised character in input: ~s~%" else) (turn n)])]))
(turn 0))

```

{{out}}

```txt
(play 3)
turn #0
123 | 123
--- | ---
a 001 | 101
b 110 | 101
c 100 | 000
1
flipping col 1
turn #1
123 | 123
--- | ---
a 101 | 101
b 010 | 101
c 000 | 000
b
flipping row 2
you won on turn #2
```

## REXX

This REXX version allows the specification (on the invocation line) for: :::* the size of the array (grid) [the default is '''3''', the maximum is '''26'''] :::* the number of bits (for the target) to be flipped is the size of the grid (the whole row or column)

Programming note: none of the command line parameters ('''N''' and '''u''') are checked for errors (so as to make the

program simpler). A fair amount of coding was added to check for a legal "move".

```/*REXX program presents a  "flipping bit"  puzzle.  The user can solve via it via  C.L. */
parse arg  N u seed .                            /*get optional arguments from the C.L. */
if N==''  |  N==","     then N=3                 /*Size given?   Then use default of  3.*/
if u==''  |  u==","     then u=N                 /*the number of bits initialized to ON.*/
if datatype(seed, 'W')  then call random ,,seed  /*is there a seed (for repeatability?) */
col@= 'a b c d e f g h i j k l m n o p q r s t u v w x y z'     /*literal for column id.*/
cols=space(col@, 0);        upper cols           /*letters to be used for the columns.  */
@.=0;  !.=0                                      /*set both arrays to  "off" characters.*/
tries=0                                          /*number of player's attempts (so far).*/
do  while  show(0) < u                  /* [↓]   turn  "on"  U  number of bits.*/
r=random(1, N);      c=random(1, N)     /*get a random  row  and  column.      */
@.r.c=1       ;      !.r.c=1            /*set (both)  row and column  to ON.   */
end   /*while*/                         /* [↑]  keep going 'til   U   bits set.*/
oz=z                                             /*save the original array string.      */
call show 1, '   ◄═══target═══╣', , 1            /*display the target for user to attain*/
do random(1,2); call flip 'R',random(1,N) /*flip a   row    of  bits.            */
call flip 'C',random(1,N) /*  "  "  column   "    "              */
end   /*random*/                          /* [↑]  just perform  1  or  2  times. */
if z==oz  then call flip 'R', random(1, N)       /*ensure it's not target we're flipping*/
do  until  z==oz;      call prompt        /*prompt until they get it right.      */
call flip left(?, 1),  substr(?, 2)       /*flip a user selected row or column.  */
call show 0                               /*get image (Z) of the updated array.  */
end   /*until*/
call show 1, '   ◄───your array'                 /*display the array to the terminal.   */
say '─────────Congrats!    You did it in'     tries     "tries."
exit tries                                       /*stick a fork in it,  we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
halt:  say 'program was halted by user.';  exit  /*the REXX program was halted by user. */
hdr:   aaa=arg(1);  if oo==1  then aaa=translate(aaa, "╔═║", '┌─│');    say aaa;    return
isInt: return datatype( arg(1), 'W')             /*returns   1   if  arg  is an integer.*/
isLet: return datatype( arg(1), 'M')             /*returns   1   if  arg  is a letter.  */
terr:  if ok  then say  '───────── ***error***:  illegal'  arg(1);        ok=0;     return
/*──────────────────────────────────────────────────────────────────────────────────────*/
flip: arg x,#;   do c=1  for N  while x=='R';  @.#.c = \@.#.c;  end  /*c*/
do r=1  for N  while x=='C';  @.r.# = \@.r.#;  end  /*r*/;         return
/*──────────────────────────────────────────────────────────────────────────────────────*/
prompt: if tries\==0  then  say '─────────bit array after play: '         tries
signal on halt                           /*another method for the player to quit*/
!='─────────Please enter a    row number    or a    column letter,      or  Quit:'
call show 1, '   ◄───your array'         /*display the array to the terminal.   */
do forever  until ok;       ok=1;     say;     say !;     pull ?  _  .  1  aa
if abbrev('QUIT', ?, 1)     then do;  say '─────────quitting···';  exit 0;  end
if ?==''                    then do;  call show 1,"   ◄═══target═══╣",.,1; ok=0
end                       /* [↑] reshow targ*/
if _ \== ''                 then call terr 'too many args entered:'   aa
if \isInt(?) & \isLet(?)    then call terr 'row/column: '             ?
if  isLet(?)                then a=pos(?, cols)
if  isLet(?) & (a<1 | a>N | length(?)>1)  then call terr 'column: '   ?
if  isLet(?)                then ?='C'pos(?, cols)
if  isInt(?) & (?<1 | ?>N)  then call terr 'row: '                    ?
if  isInt(?)                then ?='R' || (?/1)            /*normalize number*/
end   /*forever*/                                          /*end of da checks*/
tries= tries + 1                                              /*bump da counter.*/
return ?                                                      /*return response.*/
/*──────────────────────────────────────────────────────────────────────────────────────*/
show: \$=0;              _=;            parse arg tell,tx,o,oo         /*\$≡num of ON bits*/
if tell  then do; say;     say '     '   subword(col@, 1, N)   "  column letter"
call hdr 'row ┌'copies('─', N+N+1)            /*prepend col hdrs*/
end                                               /* [↑]  grid hdrs.*/
z=                                                              /* [↓] build grid.*/
do   r=1  for N                                               /*show  grid rows.*/
do c=1  for N;  if o==.  then do;  z=z || !.r.c;  _=_ !.r.c;  \$=\$ + !.r.c;   end
else do;  z=z || @.r.c;  _=_ @.r.c;  \$=\$ + @.r.c;   end
end   /*c*/                                                 /*··· and sum ONs.*/
if tx\==''  then tar.r=_ tx                                   /*build da target?*/
if tell     then call hdr right(r, 2)   ' │'_   tx; _=        /*show the grid?  */
end     /*r*/                                                 /*show a grid row.*/
if tell  then say;                     return \$                 /*show blank line?*/
```

{{out|output|text= when using the default input of: 3 }}

Note that the user's input is also shown (annotated).

Also note that the 2nd answer was a blank (or nothing), which caused the program to re-show the target array.

```
a b c   column letter
row ╔═══════
1  ║ 0 1 0    ◄═══target═══╣
2  ║ 0 0 0    ◄═══target═══╣
3  ║ 0 1 1    ◄═══target═══╣

a b c   column letter
row ┌───────
1  │ 1 0 0    ◄───your array
2  │ 1 1 0    ◄───your array
3  │ 0 1 0    ◄───your array

─────────Please enter a    row number    or a    column letter,      or  Quit:
b                                    ◄■■■■■■■■■■■■■ user input
─────────bit array after play:  1

a b c   column letter
row ┌───────
1  │ 1 1 0    ◄───your array
2  │ 1 0 0    ◄───your array
3  │ 0 0 0    ◄───your array

─────────Please enter a    row number    or a    column letter,      or  Quit:
a                                    ◄■■■■■■■■■■■■■ user input

─────────bit array after play:  2

a b c   column letter
row ┌───────
1  │ 0 1 0    ◄───your array
2  │ 0 0 0    ◄───your array
3  │ 1 0 0    ◄───your array

─────────Please enter a    row number    or a    column letter,      or  Quit:
3                                    ◄■■■■■■■■■■■■■ user input

a b c   column letter
row ┌───────
1  │ 0 1 0    ◄───your array
2  │ 0 0 0    ◄───your array
3  │ 0 1 1    ◄───your array

─────────Congrats!    You did it in 3 tries.

```

{{out|output|text= when using the following was used for input: 5 }}

```
a b c d e   column letter
row ╔═══════════
1  ║ 1 0 0 0 0    ◄═══target═══╣
2  ║ 1 0 0 0 0    ◄═══target═══╣
3  ║ 1 0 0 0 0    ◄═══target═══╣
4  ║ 0 0 0 0 0    ◄═══target═══╣
5  ║ 0 0 1 1 0    ◄═══target═══╣

a b c d e   column letter
row ┌───────────
1  │ 0 0 1 1 0    ◄───your array
2  │ 1 1 0 0 1    ◄───your array
3  │ 1 1 0 0 1    ◄───your array
4  │ 0 1 0 0 1    ◄───your array
5  │ 0 1 1 1 1    ◄───your array

─────────Please enter a    row number    or a    column letter,      or  Quit:
q
─────────quitting···

```

## Ring

```

size = 3
flip = newlist(size,size)
board = newlist(size,size)
colflip = list(size)
rowflip = list(size)

new qapp
{
win1 = new qwidget() {
setwindowtitle("Flipping bits game")
setgeometry(465,115,800,600)
label1 = new qlabel(win1) {
setgeometry(285,60,120,40)
settext("Target")
}
label2 = new qlabel(win1) {
setgeometry(285,220,120,40)
settext("Board")
}
for n = 1 to size
for m = 1 to size
flip[n][m] = new qpushbutton(win1) {
setgeometry(200+n*40,60+m*40,40,40)
settext(string(random(1)))
}
next
next
for n = 1 to size
for m = 1 to size
board[n][m] = new qpushbutton(win1) {
setgeometry(200+n*40,260+m*40,40,40)
setclickevent("draw(" + n + "," + m +")")
}
next
next
for n = 1 to size
colflip[n]= new qpushbutton(win1) {
setgeometry(200+n*40,260,40,40)
settext("Go")
setclickevent("coldraw(" + n + ")")
}
next
for n = 1 to size
rowflip[n]= new qpushbutton(win1) {
setgeometry(200,260+n*40,40,40)
settext("Go")
setclickevent("rowdraw(" + n + ")")
}
next
scramblebutton = new qpushbutton(win1) {
setgeometry(240,460,120,40)
settext("Scramble Board")
setclickevent("scramble(flip)")
}
scramblebegin(flip)
show()
}
exec()
}

func coldraw(n)
for row = 1 to size
board[n][row] {temp = text()}
if temp = "0"
board[n][row].settext("1")
else
board[n][row].settext("0")
ok
next

func rowdraw(n)
for col = 1 to size
board[col][n] {temp = text()}
if temp = "0"
board[col][n].settext("1")
else
board[col][n].settext("0")
ok
next

func scramble(flip)
for col = 1 to size
for row = 1 to size
flip[col][row]{temp = text()}
board[col][row].settext(temp)
next
next
for mix = 1 to size*10
colorrow = random(1) + 1
colrow = random(size-1) + 1
if colorrow = 1
rc = "coldraw"
else
rc = "rowdraw"
ok
go = rc + "(" + colrow + ")"
eval(go)
next

func scramblebegin(flip)
for col = 1 to size
for row = 1 to size
flip[col][row]{temp = text()}
board[col][row].settext(temp)
next
next

```

Output:

[https://1drv.ms/v/s!AqDUIunCqVnIg1Tbq1vXuLSg5B6L Flipping bits game]

## Ruby

```class FlipBoard
def initialize(size)
raise ArgumentError.new("Invalid board size: #{size}") if size < 2

@size = size
@board = Array.new(size**2, 0)

randomize_board
loop do
@target = generate_target
break unless solved?
end

# these are used for validating user input
@columns = [*'a'...('a'.ord+@size).chr]
@rows = (1..@size).map(&:to_s)
end

############################################################

def play
moves = 0

until solved?
puts "", "move #{moves}:", self
print "Row/column to flip: "
ans = \$stdin.gets.strip

if @columns.include? ans
flip_column @columns.index(ans)
moves += 1
elsif @rows.include? ans
flip_row @rows.index(ans)
moves += 1
else
puts "invalid input: " + ans
end
end

puts "", "you solved the game in #{moves} moves", self
end

# the target formation as a string
def target
format_array @target
end

# the current formation as a string
def to_s
format_array @board
end

############################################################
private

def solved?
@board == @target
end

# flip a random number of bits on the board
def randomize_board
(@size + rand(@size)).times do
flip_bit rand(@size), rand(@size)
end
end

# generate a random number of flip_row/flip_column calls
def generate_target
orig_board = @board.clone
(@size + rand(@size)).times do
rand(2).zero? ? flip_row( rand(@size) ) : flip_column( rand(@size) )
end
target, @board = @board, orig_board
target
end

def flip_row(row)
@size.times {|col| flip_bit(row, col)}
end

def flip_column(col)
@size.times {|row| flip_bit(row, col)}
end

def flip_bit(row, col)
@board[@size * row + col] ^= 1
end

def format_array(ary)
str = "   " + @columns.join(" ") + "\n"
@size.times do |row|
str << "%2s " % @rows[row] + ary[@size*row, @size].join(" ") + "\n"
end
str
end
end

######################################################################
begin
FlipBoard.new(ARGV.shift.to_i).play
rescue => e
puts e.message
end
```

Sample game:

```
\$ ruby flipping_bits.rb 3
a b c
1 1 0 1
2 0 1 1
3 0 1 0

move 0:
a b c
1 0 0 1
2 0 0 0
3 0 0 1
Row/column to flip: 1

move 1:
a b c
1 1 1 0
2 0 0 0
3 0 0 1
Row/column to flip: b

move 2:
a b c
1 1 0 0
2 0 1 0
3 0 1 1
Row/column to flip: c

you solved the game in 3 moves
a b c
1 1 0 1
2 0 1 1
3 0 1 0

```

## Scala

### Java Swing Interoperability

```import java.awt.{BorderLayout, Color, Dimension, Font, Graphics, Graphics2D, Rectangle, RenderingHints}

import javax.swing.{JFrame, JPanel}

object FlippingBitsGame extends App {

class FlippingBitsGame extends JPanel {
private val maxLevel: Int = 7
private val box: Rectangle = new Rectangle(120, 90, 400, 400)

private var n: Int = maxLevel

private var grid: Array[Array[Boolean]] = _
private var target: Array[Array[Boolean]] = _

private var solved: Boolean = true

override def paintComponent(gg: Graphics): Unit = {
def drawGrid(g: Graphics2D): Unit = {
else g.drawString("Click next to a row or a column to flip.", 170, 600)
val size: Int = box.width / n
for {r <- 0 until n
c <- 0 until n} {
g.setColor(if (grid(r)(c)) Color.blue else Color.orange)
g.fillRect(box.x + c * size, box.y + r * size, size, size)
g.setColor(getBackground)
g.drawRect(box.x + c * size, box.y + r * size, size, size)
g.setColor(if (target(r)(c)) Color.blue else Color.orange)
g.fillRect(7 + box.x + c * size, 7 + box.y + r * size, 10, 10)
}
}

super.paintComponent(gg)
val g: Graphics2D = gg.asInstanceOf[Graphics2D]
g.setRenderingHint(RenderingHints.KEY_ANTIALIASING, RenderingHints.VALUE_ANTIALIAS_ON)
drawGrid(g)
}

private def printGrid(msg: String, g: Array[Array[Boolean]]): Unit = {
println(msg)
for (row <- g) println(row.mkString(", "))
println()
}

private def startNewGame(): Unit = {
val rand = scala.util.Random

if (solved) {
val minLevel: Int = 3
n = if (n == maxLevel) minLevel else n + 1
grid = Array.ofDim[Boolean](n, n)
target = Array.ofDim[Boolean](n, n)

do {
def shuffle(): Unit = for (i <- 0 until n * n)
if (rand.nextBoolean()) flipRow(rand.nextInt(n)) else flipCol(rand.nextInt(n))

shuffle()
for (i <- grid.indices) grid(i).copyToArray(target(i)) //, n)
shuffle()
} while (solved(grid, target))
solved = false
printGrid("The target", target)
printGrid("The board", grid)
}
}

private def solved(a: Array[Array[Boolean]], b: Array[Array[Boolean]]): Boolean =
a.indices.forall(i => a(i) sameElements b(i))

private def flipRow(r: Int): Unit = for (c <- 0 until n) grid(r)(c) ^= true

private def flipCol(c: Int): Unit = for (row <- grid) row(c) ^= true

setPreferredSize(new Dimension(640, 640))
setBackground(Color.white)
setFont(new Font("SansSerif", Font.PLAIN, 18))
startNewGame()
override def mousePressed(e: MouseEvent): Unit = {
if (solved) startNewGame()
else {
val x: Int = e.getX
val y: Int = e.getY
if (box.contains(x, y)) return
if (x > box.x && x < box.x + box.width) flipCol((x - box.x) / (box.width / n))
else if (y > box.y && y < box.y + box.height) flipRow((y - box.y) / (box.height / n))
solved = solved(grid, target)
printGrid(if (solved) "Solved!" else "The board", grid)
}
repaint()
}
})

}

new JFrame("Flipping Bits Game") {
pack()
setDefaultCloseOperation(javax.swing.WindowConstants.EXIT_ON_CLOSE)
setLocationRelativeTo(null)
setResizable(false)
setVisible(true)
}

}
```

{{output?|Scala}}

## Swift

{{works with|Swift 2.0}}

```import Foundation

struct Board: Equatable, CustomStringConvertible {
let size: Int
private var tiles: [Bool]

init(size: Int) {
self.size = size
tiles = Array(count: size * size, repeatedValue: false)
}

subscript(x: Int, y: Int) -> Bool {
get {
return tiles[y * size + x]
}
set {
tiles[y * size + x] = newValue
}
}

mutating func randomize() {
for i in 0..<tiles.count {
tiles[i] = Bool(random() % 2)
}
}

mutating func flipRow(row: Int) {
for i in 0..<size {
self[row, i] = !self[row, i]
}
}

mutating func flipColumn(column: Int) {
for i in 0..<size {
self[i, column] = !self[i, column]
}
}

var description: String {
var desc = "\n\ta\tb\tc\n"
for i in 0..<size {
desc += "\(i+1):\t"
for j in 0..<size {
desc += "\(Int(self[i, j]))\t"
}
desc += "\n"
}

return desc
}
}

func ==(lhs: Board, rhs: Board) -> Bool {
return lhs.tiles == rhs.tiles
}

class FlippingGame: CustomStringConvertible {

var board: Board
var target: Board
var solved: Bool { return board == target }

init(boardSize: Int) {
target = Board(size: 3)
board = Board(size: 3)
generateTarget()
}

func generateTarget() {
target.randomize()
board = target
let size = board.size
while solved {
for _ in 0..<size + (random() % size + 1) {
if random() % 2 == 0 {
board.flipColumn(random() % size)
}
else {
board.flipRow(random() % size)
}
}
}
}

func getMove() -> Bool {
print(self)
print("Flip what? ", terminator: "")

guard
where move.characters.count == 1
else { return false }

var moveValid = true

if let row = Int(move) {
board.flipRow(row - 1)
}
else if let column = move.lowercaseString.utf8.first where column < 100 && column > 96  {
board.flipColumn(numericCast(column) - 97)
}
else {
moveValid = false
}

return moveValid
}

var description: String {
var str = ""
print("Target: \n \(target)", toStream: &str)
print("Board: \n \(board)", toStream: &str)

return str
}
}

func playGame(game: FlippingGame) -> String {
game.generateTarget()
var numMoves = 0
while !game.solved {
numMoves++
print("Move #\(numMoves)")
while !game.getMove() {}
}
print("You win!")
print("Number of moves: \(numMoves)")
print("\n\nPlay Again? ", terminator: "")

}

let game = FlippingGame(boardSize: 3)
repeat { } while playGame(game) == "y"

```

{{Out}}

```
Move #1
Target:

a	b	c
1:	1	1	0
2:	0	0	1
3:	1	0	1

Board:

a	b	c
1:	0	1	0
2:	1	0	1
3:	0	0	1

Flip what? a
You win!
Number of moves: 1

Play Again? n

```

## Tcl

{{works with|Tcl|8.6}}

```package require Tcl 8.6

oo::class create Flip {
variable board target s
constructor {size} {
set s \$size
set target [my RandomConfiguration]
set board \$target
while {\$board eq \$target} {
for {set i 0} {\$i < \$s} {incr i} {
if {rand()<.5} {
my SwapRow \$i
}
if {rand()<.5} {
my SwapColumn \$i
}
}
}
}

method RandomConfiguration {{p 0.5}} {
for {set row 0} {\$row < \$s} {incr row} {
set r {}
for {set col 0} {\$col < \$s} {incr col} {
lappend r [expr {rand() < \$p}]
}
lappend result \$r
}
return \$result
}

method SwapRow {rowId} {
for {set i 0} {\$i < \$s} {incr i} {
lset board \$rowId \$i [expr {![lindex \$board \$rowId \$i]}]
}
}
method SwapColumn {columnId} {
for {set i 0} {\$i < \$s} {incr i} {
lset board \$i \$columnId [expr {![lindex \$board \$i \$columnId]}]
}
}

method Render {configuration {prefixes {}}} {
join [lmap r \$configuration p \$prefixes {
format %s%s \$p [join [lmap c \$r {string index ".X" \$c}] ""]
}] "\n"
}
method GetInput {prompt} {
puts -nonewline "\${prompt}: "
flush stdout
gets stdin
}

method play {} {
set p0 {}
set p {}
set top [format "%*s " [string length \$s] ""]
for {set i 1;set j 97} {\$i<=\$s} {incr i;incr j} {
append top [format %c \$j]
lappend p [format "%*d " [string length \$s] \$i]
lappend p0 [format "%*s " [string length \$s] ""]
}

set moves 0
puts "You are trying to get to:\n[my Render \$target \$p0]\n"
while true {
puts "Current configuration (#\$moves):\n\$top\n[my Render \$board \$p]"

# Test for if we've won
if {\$board eq \$target} break

# Ask the user for a move
set i [my GetInput "Pick a column (letter) or row (number) to flip"]

# Parse the move and apply it
if {[string is lower -strict \$i] && [set c [expr {[scan \$i "%c"] - 97}]]<\$s} {
my SwapColumn \$c
incr moves
} elseif {[string is integer -strict \$i] && \$i>0 && \$i<=\$s} {
my SwapRow [expr {\$i - 1}]
incr moves
} else {
}
puts ""
}
puts "\nYou win! (You took \$moves moves.)"
}
}

Flip create flip 3
flip play

```

{{out|Example game}}

```
You are trying to get to:
.XX
XXX
X.X

Current configuration (#0):
abc
1 .X.
2 ..X
3 X..
Pick a column (letter) or row (number) to flip: 2

Current configuration (#1):
abc
1 .X.
2 XX.
3 X..
Pick a column (letter) or row (number) to flip: c

Current configuration (#2):
abc
1 .XX
2 XXX
3 X.X

You win! (You took 2 moves.)

```