⚠️ 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.

;Task: Write a ''player'' of the [[Bulls and cows|Bulls and Cows game]], rather than a scorer. The player should give intermediate answers that respect the scores to previous attempts.

One method is to generate a list of all possible numbers that could be the answer, then to prune the list by keeping only those numbers that would give an equivalent score to how your last guess was scored. Your next guess can be any number from the pruned list.

Either you guess correctly or run out of numbers to guess, which indicates a problem with the scoring.

• [[Bulls and cows]]
• [[Guess the number]]
• [[Guess the number/With Feedback (Player)]]

```with Ada.Text_IO;

procedure Bulls_Player is

-- package for In-/Output of natural numbers
package Nat_IO is new Ada.Text_IO.Integer_IO (Natural);

-- for comparing length of the vectors

-- number of digits
Guessing_Length : constant := 4;

-- digit has to be from 1 to 9
type Digit is range 1 .. 9;
-- a sequence has specified length of digits
type Sequence is array (1 .. Guessing_Length) of Digit;

-- data structure to store the possible answers
(Element_Type => Sequence,
Index_Type   => Positive);

-- check if sequence contains each digit only once
function Is_Valid (S : Sequence) return Boolean is
Appeared : array (Digit) of Boolean := (others => False);
begin
for I in S'Range loop
if Appeared (S (I)) then
return False;
end if;
Appeared (S (I))  := True;
end loop;
return True;
end Is_Valid;

-- calculate all possible sequences and store them in the vector
procedure Fill_Pool (Pool : in out Sequence_Vectors.Vector) is
Finished : exception;
-- count the sequence up by one
function Next (S : Sequence) return Sequence is
Result : Sequence := S;
Index  : Positive := S'Last;
begin
loop
-- overflow at a position causes next position to increase
if Result (Index) = Digit'Last then
Result (Index) := Digit'First;
-- overflow at maximum position
-- we have processed all possible values
if Index = Result'First then
raise Finished;
end if;
Index := Index - 1;
else
Result (Index) := Result (Index) + 1;
return Result;
end if;
end loop;
end Next;
X        : Sequence := (others => 1);
begin
loop
-- append all valid values
if Is_Valid (X) then
Pool.Append (X);
end if;
X := Next (X);
end loop;
exception
when Finished =>
-- the exception tells us that we have added all possible values
-- simply return and do nothing.
null;
end Fill_Pool;

-- generate a random index from the pool
function Random_Index (Pool : Sequence_Vectors.Vector) return Positive is
subtype Possible_Indexes is Positive range
Pool.First_Index .. Pool.Last_Index;
(Possible_Indexes);
Index_Gen : Index_Random.Generator;
begin
Index_Random.Reset (Index_Gen);
return Index_Random.Random (Index_Gen);
end Random_Index;

-- get the answer from the player, simple validity tests
procedure Get_Answer (S : Sequence; Bulls, Cows : out Natural) is
Valid : Boolean := False;
begin
Bulls := 0;
Cows  := 0;
while not Valid loop
-- output the sequence
Ada.Text_IO.Put ("How is the score for:");
for I in S'Range loop
end loop;
begin
Nat_IO.Get (Bulls);
Nat_IO.Get (Cows);
if Bulls + Cows <= Guessing_Length then
Valid := True;
else
end if;
exception
when others =>
null;
end;
end loop;

-- remove all sequences that wouldn't give an equivalent score
procedure Strip
(V           : in out Sequence_Vectors.Vector;
S           : Sequence;
Bulls, Cows : Natural)
is
function Has_To_Be_Removed (Position : Positive) return Boolean is
Testant    : constant Sequence := V.Element (Position);
Bull_Score : Natural           := 0;
Cows_Score : Natural := 0;
begin
for I in Testant'Range loop
for J in S'Range loop
if Testant (I) = S (J) then
-- same digit at same position: Bull!
if I = J then
Bull_Score := Bull_Score + 1;
else
Cow_Score := Cow_Score + 1;
end if;
end if;
end loop;
end loop;
return Cow_Score /= Cows or else Bull_Score /= Bulls;
end Has_To_Be_Removed;
begin
for Index in reverse V.First_Index .. V.Last_Index loop
if Has_To_Be_Removed (Index) then
V.Delete (Index);
end if;
end loop;
end Strip;

-- main routine
procedure Solve is
All_Sequences : Sequence_Vectors.Vector;
Test_Index    : Positive;
Test_Sequence : Sequence;
Bulls, Cows   : Natural;
begin
-- generate all possible sequences
Fill_Pool (All_Sequences);
loop
-- pick at random
Test_Index    := Random_Index (All_Sequences);
Test_Sequence := All_Sequences.Element (Test_Index);
-- hooray, we have it!
exit when Bulls = 4;
All_Sequences.Delete (Test_Index);
Strip (All_Sequences, Test_Sequence, Bulls, Cows);
exit when All_Sequences.Length <= 1;
end loop;
if All_Sequences.Length = 0 then
-- oops, shouldn't happen
("I give up, there has to be a bug in" &
"your scoring or in my algorithm.");
else
if All_Sequences.Length = 1 then
Ada.Text_IO.Put ("The sequence you thought has to be:");
Test_Sequence := All_Sequences.First_Element;
else
Ada.Text_IO.Put ("The sequence you thought of was:");
end if;
for I in Test_Sequence'Range loop
end loop;
end if;
end Solve;

begin
-- output blah blah
("Think of a sequence of" &
Integer'Image (Guessing_Length) &
" different digits.");
Ada.Text_IO.Put_Line ("I will try to guess it. For each correctly placed");
Ada.Text_IO.Put_Line ("digit I score 1 Bull. For each digit that is on");
Ada.Text_IO.Put_Line ("the wrong place I score 1 Cow. After each guess");
Ada.Text_IO.Put_Line ("you tell me my score.");
-- solve the puzzle
Solve;
end Bulls_Player;
```

output:

```Bulls and Cows, Your turn!

Think of a sequence of 4 different digits.
I will try to guess it. For each correctly placed
digit I score 1 Bull. For each digit that is on
the wrong place I score 1 Cow. After each guess
you tell me my score.

Let's start.

How is the score for: 8 1 7 5
Bulls:2
Cows:0
How is the score for: 4 1 6 5
Bulls:1
Cows:0
How is the score for: 3 9 7 5
Bulls:1
Cows:2
How is the score for: 9 1 7 3
Bulls:0
Cows:2
The sequence you thought has to be: 8 3 9 5
```

## AutoHotkey

```length:=4, i:=0, S:=P(9,length)

Gui, Add, Text, w83 vInfo, Think of a %length%-digit number with no duplicate digits.
Gui, Add, Edit, xm w40 vCows
Gui, Add, Button, xm w83 Default vDefault, Start
Gui, Show
Return

ButtonStart:
If Default = Restart
Gui, Submit, NoHide
GuiControl, Focus, Bulls
If (Bulls = length)
{
GuiControl, , Info, Guessed in %i% tries!
GuiControl, , Default, Restart
Default = Restart
}
Else
{
If i = 0
{
GuiControl, , Default, Submit
GuiControl, , History
}
Else
{
If (StrLen(Bulls) != 1 || StrLen(Cows) != 1)
Return
If Bulls is not digit
Return
If Cows is not digit
Return
GuiControl, , History, % History .= ": " Bulls " Bulls " Cows " Cows`n"
GuiControl, , Bulls
GuiControl, , Cows

S:=Remove(S, Guess, Bulls, Cows)
}
If !S
{
GuiControl, , Info, Invalid response.
GuiControl, , Default, Restart
Default = Restart
}
Else
{
Guess := SubStr(S,1,length)
GuiControl, , History, % History . Guess
GuiControl, , Info, Enter a single digit number of bulls and cows.
i++
}
}
Return

GuiEscape:
GuiClose:
ExitApp

Remove(S, Guess, Bulls, Cows) {
Loop, Parse, S, `n
If (Bulls "," Cows = Response(Guess, A_LoopField))
S2 .= A_LoopField . "`n"
Return SubStr(S2,1,-1)
}

; from http://rosettacode.org/wiki/Bulls and Cows#AutoHotkey
Response(Guess,Code) {
Bulls := 0, Cows := 0
Loop, % StrLen(Code)
If (SubStr(Guess, A_Index, 1) = SubStr(Code, A_Index, 1))
Bulls++
Else If (InStr(Code, SubStr(Guess, A_Index, 1)))
Cows++
Return Bulls "," Cows
}

; from http://rosettacode.org/wiki/Permutations#Alternate_Version
P(n,k="",opt=0,delim="",str="") {
i:=0
If !InStr(n,"`n")
If n in 2,3,4,5,6,7,8,9
Loop, %n%
n := A_Index = 1 ? A_Index : n "`n" A_Index
Else
Loop, Parse, n, %delim%
n := A_Index = 1 ? A_LoopField : n "`n" A_LoopField
If (k = "")
RegExReplace(n,"`n","",k), k++
If k is not Digit
Return "k must be a digit."
If opt not in 0,1,2,3
Return "opt invalid."
If k = 0
Return str
Else
Loop, Parse, n, `n
If (!InStr(str,A_LoopField) || opt & 1)
s .= (!i++ ? (opt & 2 ? str "`n" : "") : "`n" )
. P(n,k-1,opt,delim,str . A_LoopField . delim)
Return s
}
```

## BBC BASIC

```      secret\$ = ""
REPEAT
c\$ = CHR\$(&30 + RND(9))
IF INSTR(secret\$, c\$) = 0 secret\$ += c\$
UNTIL LEN(secret\$) = 4

FOR i% = 1234 TO 9876
possible\$ += STR\$(i%)
NEXT

PRINT "Guess a four-digit number with no digit used twice."
guesses% = 0
REPEAT

IF LEN(possible\$) = 4 THEN
guess\$ = possible\$
ELSE
guess\$ = MID\$(possible\$, 4*RND(LEN(possible\$) / 4) - 3, 4)
ENDIF

PRINT '"Computer guesses " guess\$
guesses% += 1

IF guess\$ = secret\$ PRINT "Correctly guessed after "; guesses% " guesses!" : END

PROCcount(secret\$, guess\$, bulls%, cows%)
PRINT "giving " ;bulls% " bull(s) and " ;cows% " cow(s)."

i% = 1
REPEAT
temp\$ = MID\$(possible\$, i%, 4)
PROCcount(temp\$, guess\$, testbulls%, testcows%)
IF bulls%=testbulls% IF cows%=testcows% THEN
i% += 4
ELSE
possible\$ = LEFT\$(possible\$, i%-1) + MID\$(possible\$, i%+4)
ENDIF
UNTIL i% > LEN(possible\$)

IF INSTR(possible\$, secret\$) = 0 STOP

UNTIL FALSE
END

DEF PROCcount(secret\$, guess\$, RETURN bulls%, RETURN cows%)
LOCAL i%, c\$
bulls% = 0
cows% = 0
FOR i% = 1 TO 4
c\$ = MID\$(secret\$, i%, 1)
IF MID\$(guess\$, i%, 1) = c\$ THEN
bulls% += 1
ELSE IF INSTR(guess\$, c\$) THEN
cows% += 1
ENDIF
ENDIF
NEXT i%
ENDPROC

```

## C

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

char *list;
const char *line = "--------+--------------------\n";
int len = 0;

int irand(int n)
{
int r, rand_max = RAND_MAX - (RAND_MAX % n);
do { r = rand(); } while(r >= rand_max);
return r / (rand_max / n);
}

char* get_digits(int n, char *ret)
{
int i, j;
char d[] = "123456789";

for (i = 0; i < n; i++) {
j = irand(9 - i);
ret[i] = d[i + j];
if (j) d[i + j] = d[i], d[i] = ret[i];
}
return ret;
}

#define MASK(x) (1 << (x - '1'))
int score(const char *digits, const char *guess, int *cow)
{
int i, bits = 0, bull = *cow = 0;

for (i = 0; guess[i] != '\0'; i++)
if (guess[i] != digits[i])
else ++bull;

while (i--) *cow += ((bits & MASK(guess[i])) != 0);

return bull;
}

void pick(int n, int got, int marker, char *buf)
{
int i, bits = 1;
if (got >= n)
strcpy(list + (n + 1) * len++, buf);
else
for (i = 0; i < 9; i++, bits *= 2) {
if ((marker & bits)) continue;
buf[got] = i + '1';
pick(n, got + 1, marker | bits, buf);
}
}

void filter(const char *buf, int n, int bull, int cow)
{
int i = 0, c;
char *ptr = list;

while (i < len) {
if (score(ptr, buf, &c) != bull || c != cow)
strcpy(ptr, list + --len * (n + 1));
else
ptr += n + 1, i++;
}
}

void game(const char *tgt, char *buf)
{
int i, p, bull, cow, n = strlen(tgt);

for (i = 0, p = 1; i < n && (p *= 9 - i); i++);
list = malloc(p * (n + 1));

pick(n, 0, 0, buf);
for (p = 1, bull = 0; n - bull; p++) {
strcpy(buf, list + (n + 1) * irand(len));
bull = score(tgt, buf, &cow);

printf("Guess %2d| %s    (from: %d)\n"
"Score   | %d bull, %d cow\n%s",
p, buf, len, bull, cow, line);

filter(buf, n, bull, cow);
}
}

int main(int c, char **v)
{
int n = c > 1 ? atoi(v) : 4;

char secret = "", answer = "";
srand(time(0));

printf("%sSecret  | %s\n%s", line, get_digits(n, secret), line);

return 0;
}
```

sample output for 4 digits:--------+-------------------- Secret | 5437 --------+-------------------- Guess 1| 7198 (from: 3024) Score | 0 bull, 1 cow --------+-------------------- Guess 2| 2386 (from: 720) Score | 0 bull, 1 cow --------+-------------------- Guess 3| 5743 (from: 122) Score | 1 bull, 3 cow --------+-------------------- Guess 4| 5437 (from: 5) Score | 4 bull, 0 cow --------+--------------------

```sample output for 9 digits<lang>--------+--------------------
Secret  | 758214936
--------+--------------------
Guess  1| 245863197    (from: 362880)
Score   | 0 bull, 9 cow
--------+--------------------
Guess  2| 964715382    (from: 133496)
Score   | 1 bull, 8 cow
--------+--------------------
Guess  3| 614927853    (from: 48722)
Score   | 0 bull, 9 cow
--------+--------------------
Guess  4| 567391248    (from: 15926)
Score   | 0 bull, 9 cow
--------+--------------------
Guess  5| 839174562    (from: 4473)
Score   | 1 bull, 8 cow
--------+--------------------
Guess  6| 489635721    (from: 1503)
Score   | 0 bull, 9 cow
--------+--------------------
Guess  7| 723156984    (from: 317)
Score   | 2 bull, 7 cow
--------+--------------------
Guess  8| 953278614    (from: 89)
Score   | 2 bull, 7 cow
--------+--------------------
Guess  9| 321479685    (from: 24)
Score   | 0 bull, 9 cow
--------+--------------------
Guess 10| 893752416    (from: 4)
Score   | 1 bull, 8 cow
--------+--------------------
Guess 11| 758214936    (from: 1)
Score   | 9 bull, 0 cow
--------+--------------------
```

## C++

```
#include <iostream>
#include <sstream>
#include <iomanip>
#include <algorithm>
#include <vector>
#include <time.h>

//--------------------------------------------------------------------------------------------------
using namespace std;

//--------------------------------------------------------------------------------------------------
const unsigned int LEN = 4;

//--------------------------------------------------------------------------------------------------
class CowsAndBulls_Player
{
public:
CowsAndBulls_Player() { fillPool(); }
void play() { secret = createSecret(); guess(); }

private:
void guess()
{
pair<int, int> res; int cc = 1;
cout << endl << " SECRET: " << secret << endl << "
### ========
" << endl;
cout << "+-----------+---------+--------+\n|   GUESS   |  BULLS  |  COWS  |\n+-----------+---------+--------+\n";
while( true )
{
string gs = gimmeANumber();
if( gs.empty() ) { cout << endl << "Something went wrong with the scoring..." << endl << "Cannot find an answer!" << endl; return; }
if( scoreIt( gs, res ) ) { cout << endl << "I found the secret number!" << endl << "It is: " << gs << endl; return; }
cout << "|    " << gs << "   |  " << setw( 3 ) << res.first << "    |  " << setw( 3 ) << res.second << "   |\n+-----------+---------+--------+\n";
clearPool( gs, res );
}
}

void clearPool( string gs, pair<int, int>& r )
{
vector<string>::iterator pi = pool.begin();
while( pi != pool.end() )
{
if( removeIt( gs, ( *pi ), r ) ) pi = pool.erase( pi );
else  pi++;
}
}

string gimmeANumber()
{
if( pool.empty() ) return "";
return pool[rand() % pool.size()];
}

void fillPool()
{
for( int x = 1234; x < 9877; x++ )
{
ostringstream oss; oss << x;
if( check( oss.str() ) ) pool.push_back( oss.str() );
}
}

bool check( string s )
{
for( string::iterator si = s.begin(); si != s.end(); si++ )
{
if( ( *si ) == '0' ) return false;
if( count( s.begin(), s.end(), ( *si ) ) > 1 ) return false;
}
return true;
}

bool removeIt( string gs, string ts, pair<int, int>& res )
{
pair<int, int> tp; getScore( gs, ts, tp );
return tp != res;
}

bool scoreIt( string gs, pair<int, int>& res )
{
getScore( gs, secret, res );
return res.first == LEN;
}

void getScore( string gs, string st, pair<int, int>& pr )
{
pr.first = pr.second = 0;
for( unsigned int ui = 0; ui < LEN; ui++ )
{
if( gs[ui] == st[ui] ) pr.first++;
else
{
for( unsigned int vi = 0; vi < LEN; vi++ )
if( gs[ui] == st[vi] ) pr.second++;
}
}
}

string createSecret()
{
string n = "123456789", rs = "";
while( rs.length() < LEN )
{
int r = rand() % n.length();
rs += n[r]; n.erase( r, 1 );
}
return rs;
}

string secret;
vector<string> pool;
};
//--------------------------------------------------------------------------------------------------
int main( int argc, char* argv[] )
{
srand( static_cast<unsigned int>( time( NULL ) ) ); CowsAndBulls_Player cb;
cb.play(); cout << endl << endl;
return system( "pause" );
}
//--------------------------------------------------------------------------------------------------

```

Output:

```
SECRET: 6281

### ========

+-----------+---------+--------+
|   GUESS   |  BULLS  |  COWS  |
+-----------+---------+--------+
|    5132   |    0    |    2   |
+-----------+---------+--------+
|    1568   |    0    |    3   |
+-----------+---------+--------+
|    2685   |    1    |    2   |
+-----------+---------+--------+
|    2816   |    0    |    4   |
+-----------+---------+--------+

I found the secret number!
It is: 6281

```

## C#

{{works with|C#|3.0}}

```
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;

namespace BullsAndCows
{
class Program
{

static IEnumerable<string> Permutations(int size)
{
if (size > 0)
{
foreach (string s in Permutations(size - 1))
foreach (char n in "123456789")
if (!s.Contains(n))
yield return s + n;
}
else
yield return "";
}

static IEnumerable<T> Shuffle<T>(IEnumerable<T> source)
{
Random random = new Random();
List<T> list = source.ToList();
while (list.Count > 0)
{
int ix = random.Next(list.Count);
yield return list[ix];
list.RemoveAt(ix);
}
}

static bool ReadBullsCows(out int bulls, out int cows)
{
bulls = cows = 0;
if (input.Length < 2)
return false;
else
return int.TryParse(input, out bulls)
&& int.TryParse(input, out cows);
}

static void Main(string[] args)
{
Console.WriteLine("Bulls and Cows");
Console.WriteLine("
### ========
");
Console.WriteLine();
{
Console.Write("My guess is {0}. How many bulls, cows? ", guess);
int bulls, cows;
Console.WriteLine("Sorry, I didn't understand that. Please try again.");
else
for (int ans = answers.Count - 1; ans >= 0; ans--)
{
int tb = 0, tc = 0;
for (int ix = 0; ix < ANSWER_SIZE; ix++)
tb++;
tc++;
if ((tb != bulls) || (tc != cows))
}
}
else
Console.WriteLine("No possible answer fits the scores you gave.");
}
}
}

```

Example output:-

```
Bulls and Cows

### ========

My guess is 7854. How many bulls, cows? 0,1
My guess is 1539. How many bulls, cows? 1,2
My guess is 2935. How many bulls, cows? 2,1
My guess is 9635. How many bulls, cows? 1,3

```

## Common Lisp

```
(defun random-number ()
(do* ((lst '(1 2 3 4 5 6 7 8 9) (remove d lst))
(l 9 (length lst))
(d (nth (random l) lst) (nth (random l) lst))
(number nil (cons d number)))
((= l 5) number)))

(defun validp (number)
(loop for el in number with rst = (rest number)
do (cond ((= el 0) (return-from validp nil))
((member el rst) (return-from validp nil))
(t (setq rst (rest rst))))
finally (return number)))

(defun bulls (number guess)
(loop for x in number
for y in guess
counting (= x y) into b
finally (return b)))

(defun bulls+cows (number guess)
(loop for x in guess
counting (member x number) into c
finally (return c)))

(defun solve ()
(let ((number (random-number))
(possible-guesses (loop for i from 1234 to 9876
when (validp (map 'list #'digit-char-p (prin1-to-string i))) collect it)))
(format t "Secret: ~a~%" number)
(loop with guess = (nth (random (length possible-guesses)) possible-guesses)
with b = (bulls number guess)
with c = (- (bulls+cows number guess) b)
do  (format t "Guess:  ~a B: ~a C: ~a~%" guess b c)
(if (= b 4)
(return-from solve (format t "Solution found!")))
(setq possible-guesses (mapcan #'(lambda (x) (if (and (= b (bulls x guess))
(= c (- (bulls+cows x guess) b)))
(list x)))
(remove guess possible-guesses)))
(setq guess (nth (random (length possible-guesses)) possible-guesses))
(setq b (bulls number guess))
(setq c (- (bulls+cows number guess) b)))))

```

Output:

```
CL-USER> (solve)
Secret: (4 8 6 1)
Guess:  (3 5 1 6) B: 0 C: 2
Guess:  (7 1 9 5) B: 0 C: 1
Guess:  (6 8 3 7) B: 1 C: 1
Guess:  (5 8 4 3) B: 1 C: 1
Guess:  (1 8 6 4) B: 2 C: 2
Guess:  (4 8 6 1) B: 4 C: 0
Solution found!
NIL

```

## Crystal

{{trans|Ruby}}

```size = 4
scores = [] of Tuple(Int32, Int32)
guesses = [] of Array(Char)
puts "Playing Bulls & Cows with #{size} unique digits."
possible_guesses = ('1'..'9').to_a.permutations(size).shuffle

loop do
guesses << (current_guess = possible_guesses.pop)
print "Guess #{guesses.size} (#{possible_guesses.size}) is #{current_guess.join}. Answer (bulls,cows)? "
bulls, cows = gets.not_nil!.split(',').map(&.to_i)
scores << (score = {bulls, cows})

# handle win
break (puts "Yeah!") if score == {size, 0}

# filter possible guesses
possible_guesses.select! do |guess|
bulls = guess.zip(current_guess).count { |g, cg| g == cg }
cows = size - (guess - current_guess).size - bulls
{bulls, cows} == score
end

# handle 'no possible guesses left'
if possible_guesses.empty?
puts "Error in scoring?"
guesses.zip(scores).each { |g, (b, c)| puts "#{g.join} => bulls #{b} cows #{c}" }
break
end
end
```

## D

```void main() {
import std.stdio, std.random, std.algorithm, std.range, std.ascii;

immutable d9 = "123456789";
auto choices = cartesianProduct(d9, d9, d9, d9).map!(t => [t[]])
.filter!(a => a.sort().uniq.count == 4).array;

do {
const ans = choices[uniform(0, \$)];
writef("My guess is %s. How many bulls and cows? ", ans);
immutable score = readln.filter!isDigit.map!q{ a - '0' }.array;
choices = choices.remove!(c => score !=
[c.zip(ans).count!(p => p == p),
c.zip(ans).count!(p => p != p && ans.canFind(p))]);
} while (choices.length > 1);

if (choices.empty)
return "Nothing fits the scores you gave.".writeln;
writeln("Solution found: ", choices);
}
```

{{out|Example output}}

```My guess is 9345. How many bulls and cows? 02
My guess is 8496. How many bulls and cows? 01
My guess is 2739. How many bulls and cows? 12
My guess is 3129. How many bulls and cows? 03
My guess is 7931. How many bulls and cows? 40
Solution found: 7931
```

## Elixir

{{works with|Elixir|1.2}}

```defmodule Bulls_and_cows do
def player(size \\ 4) do
possibility = permute(size) |> Enum.shuffle
player(size, possibility, 1)
end

def player(size, possibility, i) do
guess = hd(possibility)
IO.puts "Guess #{i} is #{Enum.join(guess)}  (from #{length(possibility)} possibilities)"
case get_score(size) do
{^size, 0} -> IO.puts "Solved!"
score ->
case select(size, possibility, guess, score) do
[] -> IO.puts "Sorry! I can't find a solution. Possible mistake in the scoring."
selected -> player(size, selected, i+1)
end
end
end

defp get_score(size) do
|> String.split(~r/\D/, trim: true)
|> Enum.map(&String.to_integer/1)
|> case do
[bulls, cows] when bulls+cows in 0..size -> {bulls, cows}
_ -> get_score(size)
end
end

defp select(size, possibility, guess, score) do
Enum.filter(possibility, fn x ->
bulls = Enum.zip(x, guess) |> Enum.count(fn {n,g} -> n==g end)
cows = size - length(x -- guess) - bulls
{bulls, cows} == score
end)
end

defp permute(size), do: permute(size, Enum.to_list(1..9))
defp permute(0, _), do: [[]]
defp permute(size, list) do
for x <- list, y <- permute(size-1, list--[x]), do: [x|y]
end
end

Bulls_and_cows.player
```

{{out}}

```
Guess 1 is 6472  (from 3024 possibilities)
Guess 2 is 7321  (from 840 possibilities)
Guess 3 is 1263  (from 54 possibilities)
Guess 4 is 1234  (from 2 possibilities)
Solved!

```

## Euphoria

{{trans|C}} {{works with|Euphoria|4.*}}

```include std/sequence.e

constant line = "--------+--------------------\n"
constant digits = "123456789"
sequence list = {}

function get_digits(integer n)
integer j
sequence d = digits, ret = ""
for i=1 to n do
j = rand(length(digits)-i)
ret &= d[i+j]
if j then
d[i+j] = d[i]
d[i] = ret[i]
end if
end for
return ret
end function

return power(2,x-digits)
end function

function score(sequence pattern, sequence guess)
integer bits = 0, bull = 0, cow = 0
for i = 1 to length(guess) do
if guess[i] != pattern[i] then
else
bull += 1
end if
end for

for i = 1 to length(guess) do
end for

return {bull, cow}
end function

procedure pick(integer n, integer got, integer marker, sequence buf)
integer bits = 1
if got >= n then
list = append(list,buf)
else
for i = 0 to length(digits)-1 do
if not and_bits(marker,bits) then
buf[got+1] = i+digits
pick(n, got+1, or_bits(marker,bits), buf)
end if
bits *= 2
end for
end if
end procedure

function tester(sequence item, sequence data)
return equal(score(item,data),data)
end function

constant tester_id = routine_id("tester")

procedure game(sequence tgt)
integer p, n = length(tgt)
sequence buf = repeat(0,n), bc
list = {}
pick(n,0,0,buf)
p = 1
bc = {0,0}
while bc<n do
buf = list[rand(\$)]
bc = score(tgt,buf)
printf(1,"Guess %2d| %s    (from: %d)\nScore   | %d bull, %d cow\n%s",
{p, buf, length(list)} & bc & {line})

list = filter(list, tester_id, {buf, bc})
p+=1
end while
end procedure

constant n = 4
sequence secret = get_digits(n)
printf(1,"%sSecret  | %s\n%s", {line, secret, line})
game(secret)
```

Output:

```--------+--------------------
Secret  | 6478
--------+--------------------
Guess  1| 5813    (from: 3024)
Score   | 0 bull, 1 cow
--------+--------------------
Guess  2| 6782    (from: 720)
Score   | 1 bull, 2 cow
--------+--------------------
Guess  3| 2689    (from: 62)
Score   | 0 bull, 2 cow
--------+--------------------
Guess  4| 7562    (from: 19)
Score   | 0 bull, 2 cow
--------+--------------------
Guess  5| 6478    (from: 4)
Score   | 4 bull, 0 cow
--------+--------------------
```

## Fortran

{{works with|Fortran|90 and later}}

```module Player
implicit none

contains

subroutine Init(candidates)
integer, intent(in out) :: candidates(:)
integer :: a, b, c, d, n

n = 0
thousands: do a = 1, 9
hundreds:    do b = 1, 9
tens:          do c = 1, 9
units:           do d = 1, 9
if (b == a) cycle hundreds
if (c == b .or. c == a) cycle tens
if (d == c .or. d == b .or. d == a) cycle units
n = n + 1
candidates(n) = a*1000 + b*100 + c*10 + d
end do units
end do tens
end do hundreds
end do thousands

end subroutine init

subroutine Evaluate(bulls, cows, guess, candidates)
integer, intent(in) :: bulls, cows, guess
integer, intent(in out) :: candidates(:)
integer :: b, c, s, i, j
character(4) :: n1, n2

write(n1, "(i4)") guess
do i = 1, size(candidates)
if (candidates(i) == 0) cycle
b = 0
c = 0
write(n2, "(i4)") candidates(i)
do j = 1, 4
s = index(n1, n2(j:j))
if(s /= 0) then
if(s == j) then
b = b + 1
else
c = c + 1
end if
end if
end do
if(.not.(b == bulls .and. c == cows)) candidates(i) = 0
end do
end subroutine Evaluate

function Nextguess(candidates)
integer :: Nextguess
integer, intent(in out) :: candidates(:)
integer :: i

nextguess = 0
do i = 1, size(candidates)
if(candidates(i) /= 0) then
nextguess = candidates(i)
candidates(i) = 0
return
end if
end do
end function
end module Player

program Bulls_Cows
use Player
implicit none

integer :: bulls, cows, initial, guess
integer :: candidates(3024) = 0
real :: rnum

! Fill candidates array with all possible number combinations
call Init(candidates)

! Random initial guess
call random_seed
call random_number(rnum)
initial = 3024 * rnum + 1
guess = candidates(initial)
candidates(initial) = 0

do
write(*, "(a, i4)") "My guess is ", guess
write(*, "(a)", advance = "no") "Please score number of Bulls and Cows: "
write(*,*)
if (bulls == 4) then
write(*, "(a)") "Solved!"
exit
end if

! We haven't found the solution yet so evaluate the remaining candidates
! and eliminate those that do not match the previous score given
call Evaluate(bulls, cows, guess, candidates)

! Get the next guess from the candidates that are left
guess = Nextguess(candidates)
if(guess == 0) then
! If we get here then no solution is achievable from the scores given or the program is bugged
write(*, "(a)") "Sorry! I can't find a solution. Possible mistake in the scoring"
exit
end if
end do
end program
```

Output

```
My guess is 1528
Please score number of Bulls and Cows: 0 1

My guess is 2346
Please score number of Bulls and Cows: 0 1

My guess is 3179
Please score number of Bulls and Cows: 1 2

My guess is 3795
Please score number of Bulls and Cows: 0 2

My guess is 4971
Please score number of Bulls and Cows: 2 2

My guess is 9471
Please score number of Bulls and Cows: 4 0

Solved!
```

## Go

Notes: Strategy per the suggestion in the problem description. Check algorithm lifted from Bulls and cows program. Code here uses Go's built in map type as the container for the list of still-possible numbers; only the map key is used, the value is assigned a dummy of 0.

```package main

import (
"bufio"
"fmt"
"os"
"strconv"
"strings"
)

func main() {
fmt.Println(`Cows and bulls/player
You think of four digit number of unique digits in the range 1 to 9.
I guess.  You score my guess:
A correct digit but not in the correct place is a cow.
A correct digit in the correct place is a bull.
You give my score as two numbers separated with a space.`)

// generate possible patterns, store in map
m := make(map[string]int)
var g func([]byte, int)
g = func(digits []byte, fixed int) {
if fixed == 4 {
m[string(digits[:4])] = 0
return
}
for i := fixed; i < len(digits); i++ {
digits[fixed], digits[i] = digits[i], digits[fixed]
g(digits, fixed+1)
digits[fixed], digits[i] = digits[i], digits[fixed]
}
}
g([]byte("123456789"), 0)

// guess/score/eliminate loop
// pick a value, ie, guess
var guess string
for guess = range m {
delete(m, guess)
break
}

// get and parse score
var c, b uint
for ;; fmt.Println("Score guess as two numbers: cows bulls") {
fmt.Printf("My guess: %s.  Score? (c b) ", guess)
if err != nil {
fmt.Println("\nSo, bye.")
return
}
s2 := strings.Fields(score)
if len(s2) == 2 {
c2, err := strconv.ParseUint(s2, 10, 0)
if err == nil && c2 <= 4 {
b2, err := strconv.ParseUint(s2, 10, 0)
if err == nil && c2+b2 <= 4 {
c = uint(c2)
b = uint(b2)
break
}
}
}
}

// check for win
if b == 4 {
fmt.Println("I did it. :)")
return
}

// eliminate patterns with non-matching scores
for pat := range m {
var cows, bulls uint
for ig, cg := range guess {
switch strings.IndexRune(pat, cg) {
case -1:
default: // I just think cows should go first
cows++
case ig:
bulls++
}
}
if cows != c || bulls != b {
delete(m, pat)
}
}

// check for inconsistency
if len(m) == 0 {
fmt.Println("Oops, check scoring.")
return
}
}
}
```

```import Data.List
import System.Random (randomRIO)
import Data.Char(digitToInt)

combinationsOf 0 _ = [[]]
combinationsOf _ [] = []
combinationsOf k (x:xs) = map (x:) (combinationsOf (k-1) xs) ++ combinationsOf k xs

player = do
let ps = concatMap permutations \$ combinationsOf 4 ['1'..'9']
play ps   where

play ps =
if null ps then
putStrLn "Unable to find a solution"
else do i <- randomRIO(0,length ps - 1)
let p = ps!!i :: String
putStrLn ("My guess is " ++ p) >>  putStrLn "How many bulls and cows?"
input <- takeInput
let bc = input ::[Int]
ps' = filter((==sum bc).length. filter id. map (flip elem p))
\$ filter((==head bc).length. filter id. zipWith (==) p) ps
if length ps' == 1 then putStrLn \$ "The answer is " ++ head ps'
else play ps'

takeInput = do
inp <- getLine
let ui = map digitToInt \$ take 2 \$ filter(`elem` ['0'..'4']) inp
if sum ui > 4 || length ui /= 2 then
do putStrLn "Wrong input. Try again"
takeInput
else return ui
```

Example:

```*Main> player
My guess is 4923
How many bulls and cows?
2 2
My guess is 3924
How many bulls and cows?
1 3
My guess is 4329
How many bulls and cows?
1 3
My guess is 4932
How many bulls and cows?
4 0
```

## J

```require'misc'

poss=:1+~.4{."1 (i.!9)A.i.9
fmt=: ' ' -.~ ":

play=:3 :0
while.1<#poss=.poss do.
smoutput'guessing ',fmt guess=.({~ ?@#)poss
bc=.+/\_".prompt 'how many bull and cows? '
poss=.poss #~({.bc)=guess+/@:="1 poss
poss=.poss #~({:bc)=guess+/@e."1 poss
end.
if.#poss do.
else.
'no valid possibilities'
end.
)
```

For example:

```   play''
guessing 7461
how many bull and cows? 0 1
guessing 3215
how many bull and cows? 0 3
guessing 2357
how many bull and cows? 2 0
guessing 1359
how many bull and cows? 3 0
```

## Julia

{{works with|Julia version 0.6.0}}

```
countbulls(a, b) = sum([a[i] == b[i] for i in 1:length(a)])
countcows(a, b) = sum([a[i] == b[j] for i in 1:length(a), j in 1:length(b) if i != j])
validate(a, b) = typeof(a) == Int && typeof(b) == Int && a >= 0 && b >= 0 && a + b < 5

function doguess()
poss = [a for a in collect(Base.product(1:9,1:9,1:9,1:9)) if length(unique(a))==4]
while(length(poss) > 0)
ans = rand(poss, 1)
while true
println("My guess: \$(ans)\$(ans)\$(ans)\$(ans). How many bulls and cows?")
bul, cow = parse(Int,regres), parse(Int,regres)
if(validate(bul, cow))
break
else
println("Please enter an integer each for bulls and cows.")
end
end
if(bul == 4)
return ans
end
filter!(i -> (countbulls(ans,i), countcows(ans, i)) == (bul, cow), poss)
end
Base.throw("ERROR: No solutions found. Inconsistent scoring by other player?")
end

answ = doguess()
println("The winning pick: \$(answ)\$(answ)\$(answ)\$(answ)")

```

Example game:

```
My guess: 9517. How many bulls and cows?
0 1
My guess: 3285. How many bulls and cows?
1 1
My guess: 4298. How many bulls and cows?
0 2
My guess: 2465. How many bulls and cows?
0 2
My guess: 3926. How many bulls and cows?
2 0
My guess: 3724. How many bulls and cows?
3 0
My guess: 3124. How many bulls and cows?
4 0
The winning pick: 3124

```

## Kotlin

```// version 1.1.2

import java.util.Random

fun countBullsAndCows(guess: IntArray, answer: IntArray): Pair<Int,Int> {
var bulls = 0
var cows = 0
for ((i, d) in guess.withIndex()) {
else if (d in answer) cows++
}
return bulls to cows
}

fun main(args: Array<String>) {
val r = Random()
val choices = mutableListOf<IntArray>()
// generate all possible distinct 4 digit (1 to 9) integer arrays
for (i in 1..9) {
for (j in 1..9) {
if (j == i) continue
for (k in 1..9) {
if (k == i || k == j) continue
for (l in 1..9) {
if (l == i || l == j || l == k) continue
}
}
}
}

// pick one at random as the answer

// keep guessing, pruning the list as we go based on the score, until answer found
while (true) {
val guess = choices[r.nextInt(choices.size)]
val (bulls, cows) = countBullsAndCows(guess, answer)
println("Guess = \${guess.joinToString("")}  Bulls = \$bulls  Cows = \$cows")
if (bulls == 4) {
return
}
for (i in choices.size - 1 downTo 0) {
val (bulls2, cows2) = countBullsAndCows(choices[i], answer)
// if score is no better remove it from the list of choices
if (bulls2 <= bulls && cows2 <= cows) choices.removeAt(i)
}
if (choices.size == 0)
println("Something went wrong as no choices left! Aborting program")
}
}
```

Sample game: {{out}}

```
Guess = 7185  Bulls = 0  Cows = 2
Guess = 7862  Bulls = 1  Cows = 2
Guess = 6982  Bulls = 2  Cows = 0
Guess = 1762  Bulls = 2  Cows = 2
Guess = 1264  Bulls = 0  Cows = 3
Guess = 2761  Bulls = 1  Cows = 3
Guess = 6742  Bulls = 3  Cows = 0
Guess = 1627  Bulls = 0  Cows = 4
Guess = 6712  Bulls = 4  Cows = 0

```

## Liberty BASIC

As supplied rhe code shows the remaining pool of numbers after each guess is scored.

```
guesses    =0

do while len( secret\$) <4    '    zero not allowed    <<<<<<<<<
n\$ =chr\$( int( rnd( 1) *9) +49)
if not( instr( secret\$, n\$)) then secret\$ =secret\$ +n\$
loop

print " Secretly, my opponent just chose a number. But she didn't tell anyone!                                     "; secret\$; "."
print "     I can however be given a score for my guesses."

for i =1234 to 9876    '                    <<<<<<<<<
if check( str\$( i)) =0 then available\$ =available\$ +" " +str\$( i): k =k +1
next i

available\$ =trim\$( available\$)  '   remove the surplus, leading space

print
print "Currently holding "; k; " possible numbers. "

while 1
guess\$ =word\$( available\$, 1 +int( k *rnd( 1)), " ")
print
print "Computer guessed "; guess\$; " & got ";

bulls    =0
cows     =0
guesses  =guesses +1

r\$    =score\$( guess\$, secret\$)

bulls =val( word\$( r\$, 1, ","))
cows  =val( word\$( r\$, 2, ","))

print bulls; " bull(s), and "; cows; " cow(s), .... ";

if guess\$ =secret\$ then
print "Computer won after "; guesses; " guesses!";
secs =( time\$( "seconds") -now +86400) mod 86400
print " That took "; secs; " seconds. ENDED!"
print
print " Now scroll right to see original choice and check!"
exit while
end if

print " so possible numbers are now only..."
kk      =0
new\$    =""

for j =1 to k
bullsT    =0
cowsT     =0

possible\$ =word\$( available\$, j, " ")

r\$ =score\$( guess\$, possible\$)

bullsT =val( word\$( r\$, 1, ","))
cowsT  =val( word\$( r\$, 2, ","))

if ( bullsT =bulls) and ( cowsT =cows)  then
new\$ =new\$ +" " +possible\$    '    keep those with same score
kk =kk +1
print possible\$; " ";
if ( kk mod 20) =0 then print
end if

scan
next j

available\$ =trim\$( new\$)
k =kk

scan
wend

end

function score\$( a\$, b\$)    '   return as a csv string the number of bulls & cows.
bulls    = 0:  cows     = 0
for i = 1 to 4
c\$ = mid\$( a\$, i, 1)
if mid\$( b\$, i, 1) = c\$ then
bulls = bulls + 1
else
if instr( b\$, c\$) <>0 and instr( b\$, c\$) <>i then cows = cows + 1
end if
next i
score\$ =str\$( bulls); ","; str\$( cows)
end function

function check( i\$)
check =0    '    zero flags available: 1 means not available
for i =1 to 3
for j =i +1 to 4
if mid\$( i\$, i, 1) =mid\$( i\$, j, 1) then check =1
next j
next i
if instr( i\$, "0") then check =1
end function

```

## Mathematica

```
bullCow={Count[#1-#2,0],Length[#1\[Intersection]#2]-Count[#1-#2,0]}&;
Module[{r,input,candidates=Permutations[Range,{4}]},
While[True,
r=InputString[];
If[r===\$Canceled,Break[],
input=ToExpression/@StringSplit@r;
If[Length@input!=3,Print["Input the guess, number of bulls, number of cows, delimited by space."],
candidates=Select[candidates,bullCow[ToCharacterCode@StringJoin[ToString/@#],ToCharacterCode@ToString@input[]]==input[[2;;3]]&];
candidates=SortBy[candidates,{-3,-1}.bullCow[ToCharacterCode@StringJoin[ToString/@#],ToCharacterCode@ToString@input[]]&];
If[candidates==={},Print["No more candidates."];Break[]];
If[Length@candidates==1,Print["Must be: "<>StringJoin[ToString/@candidates[]]];Break[]];
Print[ToString@Length@candidates<>" candidates remaining."];
Print["Can try "<>StringJoin[ToString/@First@candidates]<>"."];
]]]]

```

Output:

```
120 candidates remaining.
Can try 1256.
36 candidates remaining.
Can try 1537.
5 candidates remaining.
Can try 1584.
Must be: 1639

```

## MATLAB

```function BullsAndCowsPlayer
% Plays the game Bulls and Cows as the player

% Generate list of all possible numbers
nDigits = 4;
lowVal = 1;
highVal = 9;
combs = nchoosek(lowVal:highVal, nDigits);
nCombs = size(combs, 1);
nPermsPerComb = factorial(nDigits);
gList = zeros(nCombs.*nPermsPerComb, nDigits);
for k = 1:nCombs
gList(nPermsPerComb*(k-1)+1:nPermsPerComb*k, :) = perms(combs(k, :));
end

% Prompt user
fprintf('Think of a number with:\n')
fprintf('  %d digits\n', nDigits)
fprintf('  Each digit between %d and %d inclusive\n', lowVal, highVal)
fprintf('  No repeated digits\n')
fprintf('I''ll try to guess that number and you score me:\n')
fprintf('  1 Bull per correct digit in the correct place\n')
fprintf('  1 Cow per correct digit in the wrong place\n')
pause

% Play game until all digits are correct
nBulls = 0;
nGuesses = 0;
while nBulls < 4 && ~isempty(gList)
nList = size(gList, 1);
g = gList(randi(nList), :);     % Random guess from list
fprintf('My guess: %s?\n', sprintf('%d', g))
nBulls = input('How many bulls? ');
if nBulls < 4
nCows = input('How many cows? ');
del = false(nList, 1);
for k = 1:nList
del(k) = any([nBulls nCows] ~= CountBullsCows(g, gList(k, :)));
end
gList(del, :) = [];
end
nGuesses = nGuesses+1;
end
if isempty(gList)
fprintf('That''s bull! You messed up your scoring.\n')
else
fprintf('Yay, I won! Only took %d guesses.\n', nGuesses)
end
end

function score = CountBullsCows(guess, correct)
% Checks the guessed array of digits against the correct array to find the score
% Assumes arrays of same length and valid numbers
bulls = guess == correct;
cows = ismember(guess(~bulls), correct);
score = [sum(bulls) sum(cows)];
end
```

{{out}} Secret number: 5612

```Think of a number with:
4 digits
Each digit between 1 and 9 inclusive
No repeated digits
I'll try to guess that number and you score me:
1 Bull per correct digit in the correct place
1 Cow per correct digit in the wrong place
My guess: 3489?
How many bulls? 0
How many cows? 0
My guess: 2156?
How many bulls? 0
How many cows? 4
My guess: 5621?
How many bulls? 2
How many cows? 2
My guess: 1625?
How many bulls? 1
How many cows? 3
My guess: 5612?
How many bulls? 4
Yay, I won! Only took 5 guesses.
```

Secret number: 9934

```Think of a number with:
4 digits
Each digit between 1 and 9 inclusive
No repeated digits
I'll try to guess that number and you score me:
1 Bull per correct digit in the correct place
1 Cow per correct digit in the wrong place
My guess: 4798?
How many bulls? 0
How many cows? 2
My guess: 7862?
How many bulls? 0
How many cows? 0
My guess: 9413?
How many bulls? 1
How many cows? 2
My guess: 5439?
How many bulls? 0
How many cows? 3
My guess: 9154?
How many bulls? 2
How many cows? 0
That's bull! You messed up your scoring.
```

## Perl

{{works with|Perl 5.10.0 and above}}

```#!/usr/bin/perl
use warnings;
use strict;
use v5.10;

# Build a list of all possible solutions.  The regular expression weeds
# out numbers containing zeroes or repeated digits.  See how Perl
# automatically converts numbers to strings for us, just because we
# use them as if they were strings:
my @candidates = grep {not /0 | (\d) .* \1 /x} 1234 .. 9876;

# Repeatedly prompt for input until the user supplies a reasonable score.
# The regex validates the user's input and then returns two numbers,
# \$+{BULLS} and \$+{COWS}.

(my \$guess) = @_;

for (;;) {
say "My guess: \$guess   (from ", 0+@candidates, " possibilities)";
if (<> =~ / ^ \h* (?<BULLS> \d) \h* (?<COWS> \d) \h* \$ /x and
\$+{BULLS} + \$+{COWS} <= 4) {
return (\$+{BULLS}, \$+{COWS});
}

say "Please specify the number of bulls and the number of cows";
}
}

sub score_correct(\$\$\$\$) {
my (\$a, \$b, \$bulls, \$cows) = @_;

# Count the positions at which the digits match:
my \$exact = () = grep {substr(\$a, \$_, 1) eq substr(\$b, \$_, 1)} 0 .. 3;

# Cross-match all digits in \$a against all digits in \$b, using a regex
# (specifically, a character class) instead of an explicit loop:
my \$loose = () = \$a =~ /[\$b]/g;

return \$bulls == \$exact && \$cows == \$loose - \$exact;
}

do {
# Pick a number, display it, get the score, and discard candidates
# that don't match the score:
my \$guess = @candidates[rand @candidates];
my (\$bulls, \$cows) = read_score \$guess;
@candidates = grep {score_correct \$_, \$guess, \$bulls, \$cows} @candidates;
} while (@candidates > 1);

say(@candidates?

```

Sample game:

```msl@64Lucid:~/perl\$ ./bulls-and-cows
My guess: 1869   (from 3024 possibilities)
1 0
My guess: 3265   (from 240 possibilities)
0 2
My guess: 7853   (from 66 possibilities)
1 2
My guess: 7539   (from 7 possibilities)
0 3
msl@64Lucid:~/perl\$
```

## Perl 6

{{works with|Rakudo|2018.12}} {{trans|Perl}}

```# we use the [] reduction meta operator along with the Cartesian Product
# operator X to create the Cartesian Product of four times [1..9] and then get
# all the elements where the number of unique digits is four.
my @candidates = ([X] [1..9] xx 4).grep: *.unique == 4;

repeat {
my \$guess = @candidates.pick;
@candidates .= grep: &score-correct;

# note how we declare our two subroutines within the repeat block. This
# limits the scope in which the routines are known to the scope in which
# they are needed and saves us a lot of arguments to our two routines.
sub score-correct(\$a) {
my \$exact = [+] \$a >>==<< \$guess;

# number of elements of \$a that match any element of \$b
my \$loose = +\$a.grep: any @\$guess;

return \$bulls == \$exact && \$cows == \$loose - \$exact;
}

loop {
my \$score = prompt "My guess: {\$guess.join}.\n";

if \$score ~~ m:s/^ \$<bulls>=(\d) \$<cows>=(\d) \$/
and \$<bulls> + \$<cows> <= 4 {
return +\$<bulls>, +\$<cows>;
}

say "Please specify the number of bulls and cows";
}
}
} while @candidates > 1;

say @candidates
?? "Your secret number is {@candidates.join}!"
```

{{out}}

```My guess: 4235.
2 1
My guess: 1435.
2 1
My guess: 1245.
2 1
```

## Phix

{{Trans|Euphoria}}

```constant line = " +---------+-----------------------------+-------+------+\n"
constant digits = "123456789"

return power(2,ch-'1')
end function

function score(sequence guess, sequence goal)
integer bits = 0, bulls = 0, cows = 0
for i=1 to length(guess) do
if guess[i]=goal[i] then
bulls += 1
else
end if
end for
for i=1 to length(guess) do
end for
return {bulls, cows}
end function

sequence list = {}

procedure pick(integer n, integer got, integer marker, sequence buf)
integer bits = 1
if got>=n then
list = append(list,buf)
else
for i=0 to length(digits)-1 do
if not and_bits(marker,bits) then
buf[got+1] = i+'1'
pick(n, got+1, or_bits(marker,bits), buf)
end if
bits *= 2
end for
end if
end procedure

procedure filter_list(sequence guess, integer bulls, integer cows)
integer l = length(list), idx = 0
sequence bc = {bulls,cows}
for i=1 to l do
if score(guess,list[i])=bc then
idx += 1
list[idx] = list[i]
end if
end for
list = list[1..idx]
end procedure

procedure game(sequence tgt)
integer n = length(tgt), attempt = 1, bulls = 0, cows
sequence guess
pick(n,0,0,repeat(0,n))
while bulls<n do
guess = list[rand(length(list))]
{bulls, cows} = score(guess,tgt)
printf(1," | Guess %-2d| %9s    %-14s |   %d   |   %d  |\n",
{attempt, guess, sprintf("(from %d)",length(list)), bulls, cows})
filter_list(guess, bulls, cows)
attempt += 1
end while
puts(1,line)
end procedure

constant N = 4
sequence secret = shuffle(digits)[1..N]
printf(1,"%s | Secret  | %9s                   | BULLS | COWS |\n%s", {line, secret, line})
game(secret)
```

{{out}} N=4:

```
+---------+-----------------------------+-------+------+
| Secret  |      2685                   | BULLS | COWS |
+---------+-----------------------------+-------+------+
| Guess 1 |      2951    (from 3024)    |   1   |   1  |
| Guess 2 |      6541    (from 480)     |   0   |   2  |
| Guess 3 |      1976    (from 119)     |   0   |   1  |
| Guess 4 |      3652    (from 26)      |   1   |   2  |
| Guess 5 |      2685    (from 1)       |   4   |   0  |
+---------+-----------------------------+-------+------+

```

N=9:

```
+---------+-----------------------------+-------+------+
| Secret  | 451382796                   | BULLS | COWS |
+---------+-----------------------------+-------+------+
| Guess 1 | 392815476    (from 362880)  |   1   |   8  |
| Guess 2 | 579143826    (from 133497)  |   1   |   8  |
| Guess 3 | 785614923    (from 48828)   |   0   |   9  |
| Guess 4 | 627583491    (from 18216)   |   2   |   7  |
| Guess 5 | 357182649    (from 3719)    |   3   |   6  |
| Guess 6 | 327461859    (from 321)     |   0   |   9  |
| Guess 7 | 913582746    (from 53)      |   4   |   5  |
| Guess 8 | 973285641    (from 6)       |   1   |   8  |
| Guess 9 | 451382796    (from 2)       |   9   |   0  |
+---------+-----------------------------+-------+------+

```

N=2:

```
+---------+-----------------------------+-------+------+
| Secret  |        42                   | BULLS | COWS |
+---------+-----------------------------+-------+------+
| Guess 1 |        98    (from 72)      |   0   |   0  |
| Guess 2 |        62    (from 42)      |   1   |   0  |
| Guess 3 |        52    (from 10)      |   1   |   0  |
| Guess 4 |        32    (from 4)       |   1   |   0  |
| Guess 5 |        12    (from 3)       |   1   |   0  |
| Guess 6 |        72    (from 2)       |   1   |   0  |
| Guess 7 |        42    (from 1)       |   2   |   0  |
+---------+-----------------------------+-------+------+

```

N=1:

```
+---------+-----------------------------+-------+------+
| Secret  |         7                   | BULLS | COWS |
+---------+-----------------------------+-------+------+
| Guess 1 |         3    (from 9)       |   0   |   0  |
| Guess 2 |         5    (from 8)       |   0   |   0  |
| Guess 3 |         4    (from 7)       |   0   |   0  |
| Guess 4 |         8    (from 6)       |   0   |   0  |
| Guess 5 |         6    (from 5)       |   0   |   0  |
| Guess 6 |         7    (from 4)       |   1   |   0  |
+---------+-----------------------------+-------+------+

```

## PicoLisp

```(load "@lib/simul.l")

(de bullsAndCows ()
(let Choices (shuffle (mapcan permute (subsets 4 (range 1 9))))
(use (Guess Bulls Cows)
(loop
(prinl "Guessing " (setq Guess (pop 'Choices)))
(prin "How many bulls and cows? ")
(setq Choices
(filter
'((C)
(let B (cnt = Guess C)
(and
(= Bulls B)
(= Cows (- (length (sect Guess C)) B)) ) ) )
Choices ) )
(NIL Choices "No matching solution")
(NIL (cdr Choices) (pack "The answer is " (car Choices))) ) ) ) )
```

Output:

```: (bullsAndCows)
Guessing 4217
How many bulls and cows? 0 2
Guessing 5762
How many bulls and cows? 1 1
Guessing 9372
How many bulls and cows? 0 1
Guessing 7864
How many bulls and cows? 1 2
Guessing 8754
How many bulls and cows? 0 2
```

## Prolog

Works with SWI-Prolog. Use of library clfd written by '''Markus Triska'''.

There is no algorithm. We explain to Prolog the constraints on the numbers according to the previous guesses and we let Prolog decides of the next guess.

The IA :

```:- module('ia.pl', [tirage/1]).
:- use_module(library(clpfd)).

% to store the previous guesses and the answers
:- dynamic guess/2.

% parameters of the engine

% length of the guess
proposition(4).

% Numbers of digits
% 0 -> 8
digits(8).

% tirage(-)
tirage(Ms) :-
% are there previous guesses ?
(  bagof([P, R], guess(P,R), Propositions)
->  tirage(Propositions, Ms)
;   % First try
tirage_1(Ms)),
!.

% tirage_1(-)
% We choose the first Len numbers
tirage_1(L):-
proposition(Len),
Max is Len-1,
numlist(0, Max, L).

% tirage(+,-)
tirage(L, Ms) :-
proposition(Len),
length(Ms, Len),

digits(Digits),

% The guess contains only this numbers
Ms ins 0..Digits,
all_different(Ms),

% post the constraints
maplist(placees(Ms), L),

% compute a possible solution
label(Ms).

% placees(+, +])
placees(Sol, [Prop, [BP, MP]]) :-
V #= 0,

% compute the numbers of digits in good places
compte_bien_placees(Sol, Prop, V, BP1),
BP1 #= BP,

% compute the numbers of digits inbad places
compte_mal_placees(Sol, Prop, 0, V, MP1),
MP1 #= MP.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% compte_mal_placees(+, +, +, +, -).
% @arg1 : guess to create
% @arg2 : guess already used
% @arg3 : range of the first digit of the previuos arg
% @arg4 : current counter of the digit in bad places
% @arg5 : final counter of the digit in bad places
%
%
compte_mal_placees(_, [], _, MP, MP).

compte_mal_placees(Sol, [H | T], N, MPC, MPF) :-
compte_une_mal_placee(H, N, Sol, 0,  0, VF),
MPC1 #= MPC + VF,
N1 is N+1,
compte_mal_placees(Sol, T, N1, MPC1, MPF).

% Here we check one digit of an already done guess
% compte_une_mal_placee(+, +, +, +, -).
% @arg1 : the digit
% @arg2 : range of this digit
% @arg3 : guess to create
%         we check each digit of this guess
% @arg4 : range of the digit of this guess
% @arg5 : current counter of the digit in bad places
% @arg6 : final counter of the digit in bad places
%
compte_une_mal_placee(_H, _N, [], _, TT, TT).

% digit in the same range, continue
compte_une_mal_placee(H, NH, [_H1 | T], NH, TTC, TTF) :-
NH1 is NH + 1, !,
compte_une_mal_placee(H, NH, T, NH1, TTC, TTF).

% same digit in different places
% increment the counter and continue continue
compte_une_mal_placee(H, NH, [H1 | T], NH1, TTC, TTF) :-
H #= H1,
NH \= NH1,
NH2 is NH1 + 1,
TTC1 #= TTC + 1,
compte_une_mal_placee(H, NH, T, NH2, TTC1, TTF).

compte_une_mal_placee(H, NH, [H1 | T], NH1, TTC, TTF) :-
H #\= H1,
NH2 is NH1 + 1,
compte_une_mal_placee(H, NH, T, NH2, TTC, TTF).

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%
% compte_bien_placees(+, +, +, -)
% @arg1 : guess to create
% @arg2 : previous guess
% @arg3 : current counter of the digit in good places
% @arg4 : final counter of the digit in good places
%
%
compte_bien_placees([], [], MP, MP).

compte_bien_placees([H | T], [H1 | T1], MPC, MPF) :-
H #= H1,
MPC1 #= MPC + 1,
compte_bien_placees(T, T1, MPC1, MPF).

compte_bien_placees([H | T], [H1 | T1], MPC, MPF) :-
H #\= H1,
compte_bien_placees(T, T1, MPC, MPF).

```

The code to play :

```bulls_and_cows :-
retractall('ia.pl':guess(_,_)),
retractall(coups(_)),
assert(coups(1)),

repeat,
(   tirage(Ms)
atomic_list_concat(Ms1, Guess),
retract(coups(Coup)),
Coup_1 is Coup + 1,
assert(coups(Coup_1)),
format('~w My guess ~w~n', [Coup, Guess]),
assert('ia.pl':guess(Ms, [Bulls, Cows])),
Bulls = 4
;   writeln('Sorry, I can''t find a solution !'), true).

Y is X + 1.

```

A game :

``` ?- bulls_and_cows.
1 My guess 1234
Bulls : 0.
Cows  : 0.

2 My guess 5678
Bulls : 1.
Cows  : 2.

3 My guess 5769
Bulls : 0.
Cows  : 3.

4 My guess 8695
Bulls : 0.
Cows  : 3.

5 My guess 9876
Bulls : 4.
Cows  : 0.

true .

```

## PureBasic

```#answerSize = 4
Structure history
bulls.i
cows.i
EndStructure

Protected i, cows, bulls

ForEach remainingGuesses()
bulls = 0: cows = 0
For i = 1 To #answerSize
bulls + 1
cows + 1
EndIf
Next
DeleteElement(remainingGuesses())
EndIf
Next
EndProcedure

Procedure findPermutations(List permutations.s(), elementChar.s, permSize)
Protected i, j, stackDepth, elementCount = Len(elementChar) - 1, working.s = Space(permSize), *working = @working
permSize - 1
Dim stack(permSize) ;holds index states

Dim elements(elementCount)
Dim elementChar.c(elementCount)
For i = 0 To elementCount
elementChar(i) = PeekC(@elementChar + i * SizeOf(Character))
Next

i = 0
Repeat
While i <= elementCount
If elements(i) = 0
stack(stackDepth) = i
If stackDepth = permSize
For j = 0 To permSize
PokeC(*working + j * SizeOf(Character), elementChar(stack(j)))
Next
permutations() = working
Else
elements(i) = 1
stackDepth + 1
i = 0
Continue ;skip update
EndIf
EndIf
i + 1
Wend
stackDepth - 1
If stackDepth < 0
Break
EndIf
i = stack(stackDepth) + 1
elements(i - 1) = 0
ForEver
EndProcedure

If OpenConsole()
Define guess.s, guessNum, score.s, delimeter.s
NewList remainingGuesses.s()
findPermutations(remainingGuesses(), "123456789", 4)

PrintN("Playing Bulls & Cows with " + Str(#answerSize) + " unique digits." + #CRLF\$)
Repeat
If ListSize(remainingGuesses()) = 0
PrintN(#CRLF\$ + "Solved!")
Break ;exit Repeat/Forever
EndIf

PrintN(#CRLF\$ + "BadScoring!  Nothing fits the scores you gave.")
Next
Break ;exit Repeat/Forever
Else
guessNum + 1
SelectElement(remainingGuesses(), Random(ListSize(remainingGuesses()) - 1))
guess = remainingGuesses()
DeleteElement(remainingGuesses())

Print("Guess #" + Str(guessNum) + " is " + guess + ".  What does it score (bulls, cows)?")
score = Input()
If CountString(score, ",") > 0: delimeter = ",": Else: delimeter = " ": EndIf

EndIf
ForEver

Print(#CRLF\$ + #CRLF\$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf
```

Sample output:

```Playing Bulls & Cows with 4 unique digits.

Guess #1 is 6273.  What does it score (bulls, cows)?0,2
Guess #2 is 7694.  What does it score (bulls, cows)?0,2
Guess #3 is 9826.  What does it score (bulls, cows)?0,3
Guess #4 is 2569.  What does it score (bulls, cows)?2,0
Guess #5 is 2468.  What does it score (bulls, cows)?4,0

Solved!

Press ENTER to exit
```

## Python

```from itertools import permutations
from random import shuffle

try:
raw_input
except:
raw_input = input
try:
from itertools import izip
except:
izip = zip

digits = '123456789'
size = 4

def parse_score(score):
score = score.strip().split(',')
return tuple(int(s.strip()) for s in score)

def scorecalc(guess, chosen):
bulls = cows = 0
for g,c in izip(guess, chosen):
if g == c:
bulls += 1
elif g in chosen:
cows += 1
return bulls, cows

choices = list(permutations(digits, size))
shuffle(choices)
scores  = []

print ("Playing Bulls & Cows with %i unique digits\n" % size)

while True:
ans = choices
#print ("(Narrowed to %i possibilities)" % len(choices))
score = raw_input("Guess %2i is %*s. Answer (Bulls, cows)? "
score = parse_score(score)
scores.append(score)
#print("Bulls: %i, Cows: %i" % score)
found =  score == (size, 0)
if found:
print ("Ye-haw!")
break
choices = [c for c in choices if scorecalc(c, ans) == score]
if not choices:
print ("Bad scoring? nothing fits those scores you gave:")
print ('  ' +
'\n  '.join("%s -> %s" % (''.join(an),sc)
break
```

'''Sample output'''

```Playing Bulls & Cows with 4 unique digits

Guess  1 is 1935. Answer (Bulls, cows)? 0,2
Guess  2 is 4169. Answer (Bulls, cows)? 0,3
Guess  3 is 6413. Answer (Bulls, cows)? 1,1
Guess  4 is 9612. Answer (Bulls, cows)? 1,1
Guess  5 is 9481. Answer (Bulls, cows)? 3,0
Guess  6 is 9471. Answer (Bulls, cows)? 4,0
Ye-haw!
```

If the scores are inconsistent you get output like:

```Playing Bulls & Cows with 4 unique digits

Guess  1 is 1549. Answer (Bulls, cows)? 0,0
Guess  2 is 3627. Answer (Bulls, cows)? 1,0
Bad scoring? nothing fits those scores you gave:
1549 -> (0, 0)
3627 -> (1, 0)
```

## Racket

Generate the list of possible choices. Each choice is represented as list of 4 numbers.

```#lang racket/base
(require racket/string
racket/list)

(define (permutations-getall items size)
(if (zero? size)
'(())
(for/list ([tail (in-list (permutations-getall items (- size 1)))]
#:when #t
[i (in-list items)]
#:unless (member i tail))
(cons i tail))))

(define digits  (list 1 2 3 4 5 6 7 8 9))

(define size 4)

(define all-choices (shuffle (permutations-getall digits size)))

(define (listnum->string list)
(apply string-append (map number->string list)))
```

Now define some auxiliary functions to parse the user input (with a minimum error checking) and calculate the score of another possible guess.

``` (define (parse-score score)
(if (string? score)
(let ([splited-score (string-split score ",")])
(if (= (length (string-split score ",")) 2)
(apply values (map (lambda (s) (string->number (string-trim s))) splited-score))
(values #f #f)))
(values #f #f)))

(define (calculate-score guess chosen)
(define (in-chosen x) (member x chosen))
(let ([bulls (count = guess chosen)]
[cows+bulls (count in-chosen guess)])
(values bulls (- cows+bulls bulls))))
```

Main part of the game.

```(printf "Playing Bulls & Cows with ~a unique digits\n" size)

(let loop ([choices all-choices] [num 1])
(if (null? choices)
(printf "Bad scoring! nothing fits those scores you gave.")
(let ([guess (car choices)])
#;(printf "(Narrowed to ~a possibilities)\n" (length choices))
(printf "Guess #~a is ~a. Answer: Bulls, Cows? " num (listnum->string guess))
;parse-score returns (#f #f) on errors
(if (and bulls cows)
(begin
(printf "Bulls: ~a, Cows: ~a\n" bulls cows)
(if (and (= bulls size) (= cows 0))
(printf "Ye-haw!")
(let ()
(define (equal-score? chosen)
(let-values ([(c-bulls c-cows) (calculate-score guess chosen)])
(and (= c-bulls bulls) (= c-cows cows))))
(loop (filter equal-score? choices) (+ num 1)))))
(begin
(printf "Sorry, I didn't understand that. Please try again.\n")
(loop choices num)))))))
```

'''Sample Output:'''

```Playing Bulls & Cows with 4 unique digits
Guess #1 is 3958. Answer: Bulls, Cows? 0,1
Bulls: 0, Cows: 1
Sorry, I didn't understand that. Please try again.
Guess #2 is 1364. Answer: Bulls, Cows? 2,1
Bulls: 2, Cows: 1
Guess #3 is 4362. Answer: Bulls, Cows? 0,3
Bulls: 0, Cows: 3
Guess #4 is 1234. Answer: Bulls, Cows? 4,0
Bulls: 4, Cows: 0
Ye-haw!
```

'''Sample Output: Wrong scoring'''

```Playing Bulls & Cows with 4 unique digits
Guess #1 is 7189. Answer: Bulls, Cows? 0,0
Bulls: 0, Cows: 0
Guess #2 is 2453. Answer: Bulls, Cows? 1,0
Bulls: 1, Cows: 0
Bad scoring! nothing fits those scores you gave.
```

## REXX

About a third of the REXX program deals with presentation and/or validation of answers.

```/*REXX program plays the    Bulls & Cows   game with  CBLFs (Carbon Based Life Forms).  */
parse arg ? .;   if datatype(?,'W')  then call random ,,? /*Random seed? Make repeatable*/
L=1234;  H=9876;    call gen@                             /*generate all possibilities. */
do forever;  g=random(L,H); if @.g\==.  then leave /*obtain a random 1st guess.  */
end   /*forever*/                                  /* [↑]  obtain rand 1st guess.*/
\$\$1= '───── How many bulls and cows were guessed with '; \$\$2=" ?            [─── or QUIT]"
do until #()<2 | bull==4;   say;   call ask        /*examine @ list;  get answer.*/
do ?=L  to H;     if @.?==.  then iterate      /*is this already eliminated ?*/
call bull#  ?,g                                /*obtain bulls and cows count.*/
if bull\==bulls | cow\==cows  then @.?=.       /*eliminate this possibility. */
end   /*?*/
end   /*until*/

if #==0  then do;  call serr  "At least one of your responses was invalid.";  exit;    end
say;   say "           ╔═════════════════════════════════════════════════╗"
say "           ║                                                 ║"
say "           ║   Your secret Bulls and Cows number is: " g  "  ║"
say "           ║                                                 ║"
say "           ╚═════════════════════════════════════════════════╝";           say
exit                                             /*stick a fork in it,  we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
#:     #=0;    do k=L  to H;  if @.k==.  then iterate;  #=#+1;   g=k;  end;       return #
gen@:  @.=.;   do j=L  to H;  if \rep() & pos(0, j)==0  then @.j=j;    end;       return
rep:   do k=1  for 3;  if pos(substr(j, k, 1), j, k+1)\==0  then return 1;   end; return 0
serr:  say;    say  '───── ***error***   '      !     arg(1);                     return
/*──────────────────────────────────────────────────────────────────────────────────────*/
bull#: parse arg n,q;     w=length(n);    bulls=0      /*W: # digits in N;  bull cntr=0 */
do j=1  for w;    if substr(n, j, 1) \== substr(q, j, 1)  then iterate
bulls=bulls+1;    q=overlay(., q, j)     /*bump counter;  disallow for cow*/
end   /*j*/                              /* [↑]  bull count═══════════════*/
cows=0                                          /*set the number of cows to zero.*/
do k=1  for w;    _=substr(n, k, 1);   if pos(_, q)==0  then iterate
cows=cows + 1;    q=translate(q, , _)    /*bump counter;  allow multiple #*/
end   /*k*/                              /* [↑]  cow  count═══════════════*/
return
/*──────────────────────────────────────────────────────────────────────────────────────*/
ask:   do forever; say \$\$1 g \$\$2;  pull x 1 bull cow . /*display prompt;  obtain answer.*/
select                                       /* [↑]  PULL capitalizes the args*/
when abbrev('QUIT', x, 1)  then exit         /*the user wants to quit playing.*/
when bull == ''            then != "no numbers were entered."
when cow  == ''            then != "not enough numbers were entered."
when words(x) > 2          then != "too many numbers entered: "              x
when \datatype(bull, 'W')  then != "1st number (bulls) not an integer: "    bull
when \datatype(cow , 'W')  then != "2nd number (cows) not an integer: "     cow
when bull <0 | bull >4     then != "1st number (bulls) not 0 ──► 4: "       bull
when cow  <0 | cow  >4     then != "2nd number (cows) not 0 ──► 4: "        cow
when bull + cow > 4        then != "sum of bulls and cows can't be > 4: "    x
otherwise                       !=
end   /*select*/
if !\==''  then do;  call serr;  iterate;  end  /*prompt the user and try again. */
bull=bull/1;         cow=cow/1;  return         /*normalize bulls & cows numbers.*/
end     /*forever*/
```

## Ring

```
# Project : Bulls and cows/Player

secret = ""
while len(secret) != 4
c = char(48 + random(9))
if substr(secret, c) = 0
secret = secret + c
ok
end
see "secret = " + secret + nl

possible = ""
for i = 1234 to 9876
possible = possible + string(i)
next

see "guess a four-digit number with no digit used twice." + nl
guesses = 0
while true
bulls = 0
cows = 0
if len(possible) = 4
guess = possible
else
guess = substr(possible, 4*random(len(possible) / 4) - 3, 4)
ok
see "computer guesses " + guess + nl
guesses = guesses + 1
if guess = secret
see "correctly guessed after " + guesses + " guesses!" + nl
exit
ok
if len(guess) = 4
count(secret, guess, bulls, cows)
ok
i = 1
testbulls = 0
testcows = 0
while  i <= len(possible)
temp = substr(possible, i, 4)
if len(guess) = 4
count(temp, guess, testbulls, testcows)
ok
if bulls=testbulls
if cows=testcows
i = i + 4
ok
else
possible = left(possible, i-1) + substr(possible, i+4)
ok
end
if substr(possible, secret) = 0
exit
ok
end

func count(secret, guess, bulls,  cows)
bulls = 0
cows = 0
for nr = 1 to 4
c = secret[nr]
if guess != 0
if guess[nr] = c
bulls = bulls + 1
if substr(guess, c) > 0
cows = cows + 1
ok
ok
ok
next
see "giving " + bulls + " bull(s) and " + cows  + " cow(s)." + nl
return [bulls, cows]

```

## Ruby

Ruby Version 1.9+

```size = 4
scores = []
guesses = []
puts "Playing Bulls & Cows with #{size} unique digits."
possible_guesses = [*'1'..'9'].permutation(size).to_a.shuffle

loop do
guesses << current_guess = possible_guesses.pop
print "Guess #{guesses.size} is #{current_guess.join}. Answer (bulls,cows)? "
scores << score = gets.split(',').map(&:to_i)

# handle win
break (puts "Yeah!") if score == [size,0]

# filter possible guesses
possible_guesses.select! do |guess|
bulls = guess.zip(current_guess).count{|g,cg| g == cg}
cows = size - (guess - current_guess).size - bulls
[bulls, cows] == score
end

# handle 'no possible guesses left'
if possible_guesses.empty?
puts "Error in scoring?"
guesses.zip(scores).each{|g, (b, c)| puts "#{g.join} => bulls #{b} cows #{c}"}
break
end
end
```

'''Regular output'''

```
Playing Bulls & Cows with 4 unique digits.
Guess 1 is 7158. Answer (bulls,cows)? 0,1
Guess 2 is 6843. Answer (bulls,cows)? 0,2
Guess 3 is 1439. Answer (bulls,cows)? 2,1
Guess 4 is 3479. Answer (bulls,cows)? 0,2
Guess 5 is 1234. Answer (bulls,cows)? 4,0
Yeah!

```

'''Wrong scoring'''

```
Playing Bulls & Cows with 4 unique digits.
Guess 1 is 2857. Answer (bulls,cows)? 0,0
Guess 2 is 6419. Answer (bulls,cows)? 1,0
Error in scoring?
2857 => bulls 0 cows 0
6419 => bulls 1 cows 0

```

## Scala

```
def allCombinations: Seq[List[Byte]] = {
(0 to 9).map(_.byteValue).toList.combinations(4).toList.flatMap(_.permutations)
}

def nextGuess(possible: Seq[List[Byte]]): List[Byte] = possible match {
case Nil => throw new IllegalStateException
case List(only) => only
case _ => possible(Random.nextInt(possible.size))
}

def doGuess(guess: List[Byte]): Pair[Int, Int] = {
println("My guess is " + guess);
(arr(0), arr(1))
}

def testGuess(alt: List[Byte], guess: List[Byte]): Pair[Int, Int] = {
val bulls =alt.zip(guess).filter(p => p._1 == p._2).size
val cows = guess.filter(alt.contains(_)).size - bulls
(bulls, cows)
}

def play(possible: Seq[List[Byte]]): List[Byte] = {
val curGuess = nextGuess(possible)
val bc = doGuess(curGuess)
if (bc._1 == 4) { println("Ye-haw!"); curGuess }
else
play(possible.filter(p => testGuess(p, curGuess) == bc))

}

def main(args: Array[String]) {
play(allCombinations)
}

```

{{out}}

```
My guess is List(5, 8, 2, 7)
0 1
My guess is List(1, 0, 8, 9)
1 0
My guess is List(7, 0, 4, 3)
0 2
My guess is List(4, 5, 3, 9)
1 1
My guess is List(6, 3, 7, 9)
0 1
My guess is List(1, 2, 3, 4)
4 0
Ye-haw!

```

## Sidef

```# Build a list of all possible solutions.  The regular expression weeds
# out numbers containing zeroes or repeated digits.
var candidates = (1234..9876 -> grep {|n| !("#{n}" =~ /0 | (\d) .*? \1 /x) }.map{.digits});

# Repeatedly prompt for input until the user supplies a reasonable score.
# The regex validates the user's input and then returns two numbers.
loop {
"My guess: %s   (from %d possibilities)\n" \
-> printf(guess.join, candidates.len);

if (var m = (Sys.scanln("bulls cows: ") =~ /^\h*(\d)\h*(\d)\h*\$/)) {
var (bulls, cows) = m.cap.map{.to_i}...;
bulls+cows <= 4 && return(bulls, cows);
}

say "Please specify the number of bulls and the number of cows";
}
}

func score_correct(a, b, bulls, cows) {
var (exact, loose) = (0, 0);

for i in ^4 {
a[i] == b[i] ? ++exact
: (a[i]~~b && ++loose)
}

(bulls == exact) && (cows == loose)
}

# Pick a number, display it, get the score, and discard candidates
# that don't match the score:
loop {
var guess = candidates.pick;
candidates.grep!{|n| score_correct(n, guess, bulls, cows) }
candidates.len > 1 || break
}

# Print the secret number or the error message
(
candidates.len == 1 ? ("Your secret number is: %d" % candidates.join)
)->say
```

'''Output:'''

```
My guess: 7432   (from 3024 possibilities)
bulls cows: 0 1
My guess: 9216   (from 720 possibilities)
bulls cows: 1 1
My guess: 6813   (from 128 possibilities)
bulls cows: 0 1
My guess: 9157   (from 24 possibilities)
bulls cows: 1 3

```

## Tcl

{{trans|Python}} {{tcllib|struct::list}} {{tcllib|struct::set}}

```package require struct::list
package require struct::set

proc scorecalc {guess chosen} {
set bulls 0
set cows 0
foreach g \$guess c \$chosen {
if {\$g eq \$c} {
incr bulls
} elseif {\$g in \$chosen} {
incr cows
}
}
return [list \$bulls \$cows]
}

# Allow override on command line
set size [expr {\$argc ? int(\$argv) : 4}]

set choices {}
struct::list foreachperm p [split 123456789 ""] {
struct::set include choices [lrange \$p 1 \$size]
}
set scores {}

puts "Playing Bulls & Cows with \$size unique digits\n"
fconfigure stdout -buffering none
while 1 {
set ans [lindex \$choices [expr {int(rand()*[llength \$choices])}]]
puts -nonewline \
set score [scan [gets stdin] %d,%d]
lappend scores \$score
if {\$score eq {\$size 0}} {
puts "Ye-haw!"
break
}
foreach c \$choices[set choices {}] {
if {[scorecalc \$c \$ans] eq \$score} {
lappend choices \$c
}
}
if {![llength \$choices]} {
puts "Bad scoring? nothing fits those scores you gave:"
foreach a \$answers s \$scores {
puts "  [join \$a {}] -> ([lindex \$s 0], [lindex \$s 1])"
}
break
}
}
```

'''Sample Output'''

```
Playing Bulls & Cows with 4 unique digits

Guess 1 is 8527. Answer (Bulls, cows)? 0,1
Guess 2 is 5143. Answer (Bulls, cows)? 0,2
Guess 3 is 9456. Answer (Bulls, cows)? 2,0
Guess 4 is 9412. Answer (Bulls, cows)? 2,1
Guess 5 is 9481. Answer (Bulls, cows)? 3,0
Guess 6 is 9471. Answer (Bulls, cows)? 4,0
Ye-haw!

```

```
Playing Bulls & Cows with 4 unique digits

Guess 1 is 6578. Answer (Bulls, cows)? 0,0
Guess 2 is 3241. Answer (Bulls, cows)? 1,0
Bad scoring? nothing fits those scores you gave:
6578 -> (0, 0)
3241 -> (1, 0)

```

## VBA

```
Option Explicit

Sub Main_Bulls_And_Cows_Player()
Dim collSoluces As New Collection, Elem As Variant, Soluce As String
Dim strNumber As String, cpt As Byte, p As Byte
Dim i As Byte, Bulls() As Boolean, NbBulls As Byte, Cows As Byte, Poss As Long
Const NUMBER_OF_DIGITS As Byte = 4

strNumber = CreateNb(NUMBER_OF_DIGITS)
Debug.Print "TOSS : " & StrConv(strNumber, vbUnicode)
Debug.Print "---------- START ------------"
Set collSoluces = CollOfPossibleNumbers
Poss = collSoluces.Count
For Each Elem In collSoluces
'Debug.Print "Number of possibilities : " & Poss
Debug.Print "Attempt : " & StrConv(Elem, vbUnicode)
NbBulls = 0: Soluce = Elem
ReDim Bulls(NUMBER_OF_DIGITS - 1)
For i = 1 To NUMBER_OF_DIGITS
If IsBull(strNumber, Mid(Elem, i, 1), i) Then
Bulls(i - 1) = True: NbBulls = NbBulls + 1
RemoveIfNotBull collSoluces, Mid(Elem, i, 1), i
End If
Next i
Cows = 0
For i = 1 To NUMBER_OF_DIGITS
If Not Bulls(i - 1) Then
If IsCow(collSoluces, strNumber, Mid(Elem, i, 1), p) Then
If Not Bulls(p - 1) Then Cows = Cows + 1
End If
End If
Next i
Poss = collSoluces.Count
Debug.Print "Bulls : " & NbBulls & ", Cows : " & Cows
If Poss = 1 Then Exit For
Next
Debug.Print "---------- THE END ------------"
Debug.Print "TOSS WAS : " & StrConv(strNumber, vbUnicode) & " We found : " & StrConv(Soluce, vbUnicode)
End Sub

Function CreateNb(NbDigits As Byte) As String
Dim myColl As New Collection
Dim strTemp As String
Dim bytAlea As Byte

Randomize
Do
bytAlea = Int((Rnd * 9) + 1)
On Error Resume Next
If Err <> 0 Then
On Error GoTo 0
Else
strTemp = strTemp & CStr(bytAlea)
End If
Loop While Len(strTemp) < NbDigits
CreateNb = strTemp
End Function

Function CollOfPossibleNumbers() As Collection
Dim TempColl As New Collection
Dim x As String
Dim i As Long
Dim Flag As Boolean
Dim b As Byte

For i = 1234 To 9876
Flag = False
For b = 1 To 4
x = CStr(i)
If Len(Replace(x, Mid(x, b, 1), "")) < 3 Then
Flag = True: Exit For
End If
Next
If Not Flag Then TempColl.Add x, x
Next i
Set CollOfPossibleNumbers = TempColl
End Function

Function IsBull(strgNb As String, Digit As String, place As Byte) As Boolean
IsBull = (Mid(strgNb, place, 1) = Digit)
End Function

Function IsCow(C As Collection, strgNb As String, Digit As String, place As Byte) As Boolean
If (InStr(strgNb, Digit) > 0) Then
IsCow = True: place = InStr(strgNb, Digit)
RemoveIfNotCow C, Digit
End If
End Function

Sub RemoveIfNotBull(C As Collection, Digit As String, place As Byte)
Dim E As Variant

For Each E In C
If Mid(E, place, 1) <> Digit Then C.Remove E
Next
End Sub

Sub RemoveIfNotCow(C As Collection, Digit As String)
Dim E As Variant

For Each E In C
If (InStr(E, Digit) = 0) Then C.Remove E
Next
End Sub

```

{{out}}

```TOSS : 9 2 4 7
---------- START ------------
Attempt : 1 2 3 4
Bulls : 1, Cows : 1
Attempt : 1 2 4 0
Bulls : 2, Cows : 0
Attempt : 1 2 4 3
Bulls : 2, Cows : 0
Attempt : 1 2 4 5
Bulls : 2, Cows : 0
Attempt : 1 2 4 6
Bulls : 2, Cows : 0
Attempt : 1 2 4 7
Bulls : 3, Cows : 0
Attempt : 3 2 4 7
Bulls : 3, Cows : 0
Attempt : 5 2 4 7
Bulls : 3, Cows : 0
Attempt : 6 2 4 7
Bulls : 3, Cows : 0
Attempt : 8 2 4 7
Bulls : 3, Cows : 0
Attempt : 9 2 4 7
Bulls : 4, Cows : 0
---------- THE END ------------
TOSS WAS : 9 2 4 7  We found : 9 2 4 7
```

## Yabasic

{{trans|Liberty BASIC}}

```
clear screen

guesses = 0

void = ran()

while(len(secret\$) < 4)    //    zero not allowed
n\$ = chr\$(int(ran(1) * 9) + 49)
if not(instr(secret\$, n\$)) secret\$ = secret\$ + n\$
wend

print " Secretly, my opponent just chose a number. But she didn't tell anyone!\n\t\t\t\t", secret\$, "."
print "     I can however be given a score for my guesses."

for i = 1234 to 9876
if check(str\$(i)) = 0 then
available\$ = available\$ + " " + str\$(i)
k = k +1
end if
next i

available\$ = trim\$(available\$)  //   remove the surplus, leading space

while(true)
print
print "Currently holding ", k, " possible numbers. "

guess\$ =word\$(available\$, 1 + int(k * ran(1)), " ")
print "Computer guessed ", guess\$, " & got ";

bulls = 0
cows = 0
guesses = guesses + 1

r\$ = score\$(guess\$, secret\$)

bulls = val(word\$(r\$, 1, ","))
cows  = val(word\$(r\$, 2, ","))

print bulls, " bull(s), and ", cows, " cow(s)."

if guess\$ = secret\$ then
print "\nComputer won after ", guesses, " guesses!";
print " That took ", right\$(time\$, 1), " seconds. ENDED!"
break
end if
kk = 0
new\$ = ""

for j = 1 to k
bullsT = 0
cowsT = 0

possible\$ = word\$(available\$, j, " ")

r\$ = score\$(guess\$, possible\$)

bullsT = val(word\$(r\$, 1, ","))
cowsT = val(word\$(r\$, 2, ","))

if (bullsT = bulls) and ( cowsT = cows)  then
new\$ = new\$ + " " + possible\$    //    keep those with same score
kk = kk + 1
end if
next j

available\$ = trim\$(new\$)
k = kk

wend

sub score\$(a\$, b\$)    //   return as a csv string the number of bulls & cows.
local i, c\$, bulls, cows

bulls = 0 : cows = 0
for i = 1 to 4
c\$ = mid\$(a\$, i, 1)
if mid\$(b\$, i, 1) = c\$ then
bulls = bulls + 1
else
if (instr(b\$, c\$) <> 0) and (instr(b\$, c\$) <> i) cows = cows + 1
end if
next i
return str\$(bulls) + "," + str\$(cows)
end sub

sub check(i\$)
local t, i, j

t = 0    //    zero flags available: 1 means not available
for i = 1 to 3
for j = i + 1 to 4
if mid\$(i\$, i, 1) = mid\$(i\$, j, 1) t = 1
next j
next i
if instr(i\$, "0") t = 1
return t
end sub

sub word\$(l\$, i, d\$)
local c\$(1), n

n = token(l\$, c\$(), d\$)
return c\$(i)
end sub
```

## zkl

{{trans|D}}

```d9:="123456789";
choices:=Walker.cproduct(d9,d9,d9,d9).pump(List,// lazy,-->3024, order is important
fcn(list){ s:=list.concat(); (s.unique().len()==4) and s or Void.Skip });
do{
guess:=choices[(0).random(choices.len())];
score:=ask("My guess is %s. How many bulls and cows? ".fmt(guess)).strip();
bulls,cows:=score.split("").apply("toInt");  // "12"-->(1,2)
choices=choices.filter('wrap(c){
bulls==c.zipWith('==,guess).sum(0) and  // 0 + True == 1
cows ==c.zipWith('wrap(a,b){ a!=b and guess.holds(a) },guess).sum(0)
});
}while(choices.len()>1);

if(not choices) "Nothing fits the scores you gave.".println();
else            "Solution found: ".println(choices);
```

{{out}}

```
My guess is 1842. How many bulls and cows? 12
My guess is 7824. How many bulls and cows? 11
My guess is 1425. How many bulls and cows? 12
My guess is 1294. How many bulls and cows? 30
My guess is 1264. How many bulls and cows? 30
Solution found: 1234

```

{{omit from|GUISS}}