⚠️ Warning: This is a draft ⚠️
This means it might contain formatting issues, incorrect code, conceptual problems, or other severe issues.
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{{task|Sorting Algorithms}} {{Sorting Algorithm}} {{Wikipedia|Strand sort}}
;Task: Implement the [[wp:Strand sort|Strand sort]].
This is a way of sorting numbers by extracting shorter sequences of already sorted numbers from an unsorted list.
AutoHotkey
{{works with|AutoHotkey_L}}
string =
(
-2 0 -2 5 5 3 -1 -3 5 5 0 2 -4 4 2
)
string2 := string
Loop
{
loop, parse, string, %A_space%
{
list := 1 = A_index ? A_loopfield : list
StringSplit, k, list, %A_space%
if ( k%k0% <= A_loopfield ) && ( l != "" ) && ( A_index != 1 )
list := list . " " . A_loopfield
if ( k%k0% > A_loopfield )
list := A_loopfield . " " . list , index++
l := A_loopfield
}
if ( index = 0 )
{
MsgBox % "unsorted:" string2 "`n Sorted:" list
exitapp
}
string := list, list = "", index := 0
}
esc::ExitApp
outout
## C
Strand sort using singly linked list. C99, compiled with <code>gcc -std=c99</code>
```c
#include <stdio.h>
typedef struct node_t *node, node_t;
struct node_t { int v; node next; };
typedef struct { node head, tail; } slist;
void push(slist *l, node e) {
if (!l->head) l->head = e;
if (l->tail) l->tail->next = e;
l->tail = e;
}
node removehead(slist *l) {
node e = l->head;
if (e) {
l->head = e->next;
e->next = 0;
}
return e;
}
void join(slist *a, slist *b) {
push(a, b->head);
a->tail = b->tail;
}
void merge(slist *a, slist *b) {
slist r = {0};
while (a->head && b->head)
push(&r, removehead(a->head->v <= b->head->v ? a : b));
join(&r, a->head ? a : b);
*a = r;
b->head = b->tail = 0;
}
void sort(int *ar, int len)
{
node_t all[len];
// array to list
for (int i = 0; i < len; i++)
all[i].v = ar[i], all[i].next = i < len - 1 ? all + i + 1 : 0;
slist list = {all, all + len - 1}, rem, strand = {0}, res = {0};
for (node e = 0; list.head; list = rem) {
rem.head = rem.tail = 0;
while ((e = removehead(&list)))
push((!strand.head || e->v >= strand.tail->v) ? &strand : &rem, e);
merge(&res, &strand);
}
// list to array
for (int i = 0; res.head; i++, res.head = res.head->next)
ar[i] = res.head->v;
}
void show(const char *title, int *x, int len)
{
printf("%s ", title);
for (int i = 0; i < len; i++)
printf("%3d ", x[i]);
putchar('\n');
}
int main(void)
{
int x[] = {-2,0,-2,5,5,3,-1,-3,5,5,0,2,-4,4,2};
# define SIZE sizeof(x)/sizeof(int)
show("before sort:", x, SIZE);
sort(x, sizeof(x)/sizeof(int));
show("after sort: ", x, SIZE);
return 0;
}
outout
## C++
```cpp
#include <list>
template <typename T>
std::list<T> strandSort(std::list<T> lst) {
if (lst.size() <= 1)
return lst;
std::list<T> result;
std::list<T> sorted;
while (!lst.empty()) {
sorted.push_back(lst.front());
lst.pop_front();
for (typename std::list<T>::iterator it = lst.begin(); it != lst.end(); ) {
if (sorted.back() <= *it) {
sorted.push_back(*it);
it = lst.erase(it);
} else
it++;
}
result.merge(sorted);
}
return result;
}
Clojure
(ns rosettacode.strand-sort) (defn merge-join "Produces a globally sorted seq from two sorted seqables" [[a & la :as all] [b & lb :as bll]] (cond (nil? a) bll (nil? b) all (< a b) (cons a (lazy-seq (merge-join la bll))) true (cons b (lazy-seq (merge-join all lb))))) (defn unbraid "Separates a sorted list from a sequence" [u] (when (seq u) (loop [[x & xs] u u [] s [] e x] (if (nil? x) [s u] (if (>= x e) (recur xs u (conj s x) x) (recur xs (conj u x) s e)))))) (defn strand-sort "http://en.wikipedia.org/wiki/Strand_sort" [s] (loop [[s u] (unbraid s) m nil] (if s (recur (unbraid u) (merge-join m s)) m))) (strand-sort [1, 6, 3, 2, 1, 7, 5, 3]) ;;=> (1 1 2 3 3 5 6 7)
CMake
Only for lists of integers.
# strand_sort(<output variable> [<value>...]) sorts a list of integers. function(strand_sort var) # Strand sort moves elements from _ARGN_ to _answer_. set(answer) # answer: a sorted list while(DEFINED ARGN) # Split _ARGN_ into two lists, _accept_ and _reject_. set(accept) # accept: elements in sorted order set(reject) # reject: all other elements set(p) foreach(e ${ARGN}) if(DEFINED p AND p GREATER ${e}) list(APPEND reject ${e}) else() list(APPEND accept ${e}) set(p ${e}) endif() endforeach(e) # Prepare to merge _accept_ into _answer_. First, convert both lists # into arrays, for better indexing: set(e ${answer${i}}) is faster # than list(GET answer ${i} e). set(la 0) foreach(e ${answer}) math(EXPR la "${la} + 1") set(answer${la} ${e}) endforeach(e) set(lb 0) foreach(e ${accept}) math(EXPR lb "${lb} + 1") set(accept${lb} ${e}) endforeach(e) # Merge _accept_ into _answer_. set(answer) set(ia 1) set(ib 1) while(NOT ia GREATER ${la}) # Iterate elements of _answer_. set(ea ${answer${ia}}) while(NOT ib GREATER ${lb}) # Take elements from _accept_, set(eb ${accept${ib}}) # while they are less than if(eb LESS ${ea}) # next element of _answer_. list(APPEND answer ${eb}) math(EXPR ib "${ib} + 1") else() break() endif() endwhile() list(APPEND answer ${ea}) # Take next from _answer_. math(EXPR ia "${ia} + 1") endwhile() while(NOT ib GREATER ${lb}) # Take rest of _accept_. list(APPEND answer ${accept${ib}}) math(EXPR ib "${ib} + 1") endwhile() # This _reject_ becomes next _ARGN_. If _reject_ is empty, then # set(ARGN) undefines _ARGN_, breaking the loop. set(ARGN ${reject}) endwhile(DEFINED ARGN) set("${var}" ${answer} PARENT_SCOPE) endfunction(strand_sort)
strand_sort(result 11 55 55 44 11 33 33 44 22 22) message(STATUS "${result}") # -- 11;11;22;22;33;33;44;44;55;55
Common Lisp
(defun strand-sort (l cmp) (if l (let* ((l (reverse l)) (o (list (car l))) n) (loop for i in (cdr l) do (push i (if (funcall cmp (car o) i) n o))) (merge 'list o (strand-sort n cmp) #'<)))) (let ((r (loop repeat 15 collect (random 10)))) (print r) (print (strand-sort r #'<)))
output
## D
### Using doubly linked lists
```d
import std.stdio, std.container;
DList!T strandSort(T)(DList!T list) {
static DList!T merge(DList!T left, DList!T right) {
DList!T result;
while (!left.empty && !right.empty) {
if (left.front <= right.front) {
result.insertBack(left.front);
left.removeFront();
} else {
result.insertBack(right.front);
right.removeFront();
}
}
result.insertBack(left[]);
result.insertBack(right[]);
return result;
}
DList!T result, sorted, leftover;
while (!list.empty) {
leftover.clear();
sorted.clear();
sorted.insertBack(list.front);
list.removeFront();
foreach (item; list) {
if (sorted.back <= item)
sorted.insertBack(item);
else
leftover.insertBack(item);
}
result = merge(sorted, result);
list = leftover;
}
return result;
}
void main() {
auto lst = DList!int([-2,0,-2,5,5,3,-1,-3,5,5,0,2,-4,4,2]);
foreach (e; strandSort(lst))
write(e, " ");
}
{{out}}
-4 -3 -2 -2 -1 0 0 2 2 3 4 5 5 5 5
Faster version using slices
import std.stdio, std.array; T[] strandSort(T)(const(T)[] list) pure nothrow { static T[] merge(const(T)[] left, const(T)[] right) pure nothrow { T[] res; while (!left.empty && !right.empty) { if (left.front <= right.front) { res ~= left.front; left.popFront; } else { res ~= right.front; right.popFront; } } return res ~ left ~ right; } T[] result; while (!list.empty) { auto sorted = list[0 .. 1]; list.popFront; typeof(sorted) leftover; foreach (const item; list) (sorted.back <= item ? sorted : leftover) ~= item; result = merge(sorted, result); list = leftover; } return result; } void main() { const arr = [-2, 0, -2, 5, 5, 3, -1, -3, 5, 5, 0, 2, -4, 4, 2]; arr.strandSort.writeln; }
{{out}}
[-4, -3, -2, -2, -1, 0, 0, 2, 2, 3, 4, 5, 5, 5, 5]
Elixir
{{trans|Ruby}}
defmodule Sort do def strand_sort(args), do: strand_sort(args, []) defp strand_sort([], result), do: result defp strand_sort(a, result) do {_, sublist, b} = Enum.reduce(a, {hd(a),[],[]}, fn val,{v,l1,l2} -> if v <= val, do: {val, [val | l1], l2}, else: {v, l1, [val | l2]} end) strand_sort(b, :lists.merge(Enum.reverse(sublist), result)) end end IO.inspect Sort.strand_sort [7, 17, 6, 20, 20, 12, 1, 1, 9]
{{out}}
[1, 1, 6, 7, 9, 12, 17, 20, 20]
Euphoria
function merge(sequence left, sequence right)
sequence result
result = {}
while length(left) > 0 and length(right) > 0 do
if left[$] <= right[1] then
exit
elsif right[$] <= left[1] then
return result & right & left
elsif left[1] < right[1] then
result = append(result,left[1])
left = left[2..$]
else
result = append(result,right[1])
right = right[2..$]
end if
end while
return result & left & right
end function
function strand_sort(sequence s)
integer j
sequence result
result = {}
while length(s) > 0 do
j = length(s)
for i = 1 to length(s)-1 do
if s[i] > s[i+1] then
j = i
exit
end if
end for
result = merge(result,s[1..j])
s = s[j+1..$]
end while
return result
end function
constant s = rand(repeat(1000,10))
puts(1,"Before: ")
? s
puts(1,"After: ")
? strand_sort(s)
Output:
Before: {551,746,940,903,51,18,346,417,340,502}
After: {18,51,340,346,417,502,551,746,903,940}
Go
package main import "fmt" type link struct { int next *link } func linkInts(s []int) *link { if len(s) == 0 { return nil } return &link{s[0], linkInts(s[1:])} } func (l *link) String() string { if l == nil { return "nil" } r := fmt.Sprintf("[%d", l.int) for l = l.next; l != nil; l = l.next { r = fmt.Sprintf("%s %d", r, l.int) } return r + "]" } func main() { a := linkInts([]int{170, 45, 75, -90, -802, 24, 2, 66}) fmt.Println("before:", a) b := strandSort(a) fmt.Println("after: ", b) } func strandSort(a *link) (result *link) { for a != nil { // build sublist sublist := a a = a.next sTail := sublist for p, pPrev := a, a; p != nil; p = p.next { if p.int > sTail.int { // append to sublist sTail.next = p sTail = p // remove from a if p == a { a = p.next } else { pPrev.next = p.next } } else { pPrev = p } } sTail.next = nil // terminate sublist if result == nil { result = sublist continue } // merge var m, rr *link if sublist.int < result.int { m = sublist sublist = m.next rr = result } else { m = result rr = m.next } result = m for { if sublist == nil { m.next = rr break } if rr == nil { m.next = sublist break } if sublist.int < rr.int { m.next = sublist m = sublist sublist = m.next } else { m.next = rr m = rr rr = m.next } } } return }
Output:
before: [170 45 75 -90 -802 24 2 66]
after: [-802 -90 2 24 45 66 75 170]
Haskell
-- Same merge as in Merge Sort merge :: (Ord a) => [a] -> [a] -> [a] merge [] ys = ys merge xs [] = xs merge (x : xs) (y : ys) | x <= y = x : merge xs (y : ys) | otherwise = y : merge (x : xs) ys strandSort :: (Ord a) => [a] -> [a] strandSort [] = [] strandSort (x : xs) = merge strand (strandSort rest) where (strand, rest) = extractStrand x xs extractStrand x [] = ([x], []) extractStrand x (x1 : xs) | x <= x1 = let (strand, rest) = extractStrand x1 xs in (x : strand, rest) | otherwise = let (strand, rest) = extractStrand x xs in (strand, x1 : rest)
J
{{eff note|J|/:~}}
Using merge defined at [[Sorting algorithms/Merge sort#J]]:
strandSort=: (#~ merge $:^:(0<#)@(#~ -.)) (= >./\)
Example use:
strandSort 3 1 5 4 2
1 2 3 4 5
Note: the order in which this J implementation processes the strands differs from the pseudocode currently at the wikipedia page on strand sort and matches the haskell implementation currently at the wikipedia page.
Also note that the individual strands can be seen by using ; instead of merge.
((#~ ; $:^:(0<#)@(#~ -.)) (= >./\)) 3 1 5 4 2
┌───┬───┬─┬┐
│3 5│1 4│2││
└───┴───┴─┴┘
((#~ ; $:^:(0<#)@(#~ -.)) (= >./\)) 3 3 1 2 4 3 5 6
┌─────────┬─────┬┐
│3 3 4 5 6│1 2 3││
└─────────┴─────┴┘
Java
{{works with|Java|1.6+}}
import java.util.Arrays;
import java.util.LinkedList;
public class Strand{
// note: the input list is destroyed
public static <E extends Comparable<? super E>>
LinkedList<E> strandSort(LinkedList<E> list){
if(list.size() <= 1) return list;
LinkedList<E> result = new LinkedList<E>();
while(list.size() > 0){
LinkedList<E> sorted = new LinkedList<E>();
sorted.add(list.removeFirst()); //same as remove() or remove(0)
for(Iterator<E> it = list.iterator(); it.hasNext(); ){
E elem = it.next();
if(sorted.peekLast().compareTo(elem) <= 0){
sorted.addLast(elem); //same as add(elem) or add(0, elem)
it.remove();
}
}
result = merge(sorted, result);
}
return result;
}
private static <E extends Comparable<? super E>>
LinkedList<E> merge(LinkedList<E> left, LinkedList<E> right){
LinkedList<E> result = new LinkedList<E>();
while(!left.isEmpty() && !right.isEmpty()){
//change the direction of this comparison to change the direction of the sort
if(left.peek().compareTo(right.peek()) <= 0)
result.add(left.remove());
else
result.add(right.remove());
}
result.addAll(left);
result.addAll(right);
return result;
}
public static void main(String[] args){
System.out.println(strandSort(new LinkedList<Integer>(Arrays.asList(3,1,2,4,5))));
System.out.println(strandSort(new LinkedList<Integer>(Arrays.asList(3,3,1,2,4,5))));
System.out.println(strandSort(new LinkedList<Integer>(Arrays.asList(3,3,1,2,4,3,5,6))));
}
}
Output:
[1, 2, 3, 4, 5]
[1, 2, 3, 3, 4, 5]
[1, 2, 3, 3, 3, 4, 5, 6]
jq
Most of the implementation is the "merge" function for merging two arrays. Notice that the helper function, strand, is defined here as an inner function.
# merge input array with array x by comparing the heads of the arrays
# in turn; # if both arrays are sorted, the result will be sorted:
def merge(x):
length as $length
| (x|length) as $xl
| if $length == 0 then x
elif $xl == 0 then .
else
. as $in
| reduce range(0; $xl + $length) as $z
# state [ix, xix, ans]
( [0, 0, []];
if .[0] < $length and
((.[1] < $xl and $in[.[0]] <= x[.[1]]) or .[1] == $xl)
then [(.[0] + 1), .[1], (.[2] + [$in[.[0]]]) ]
else [.[0], (.[1] + 1), (.[2] + [x[.[1]]]) ]
end
) | .[2]
end ;
def strand_sort:
# The inner function emits [strand, remainder]
def strand:
if length <= 1 then .
else
reduce .[] as $x
# state: [strand, remainder]
([ [], [] ];
if ((.[0]|length) == 0) or .[0][-1] <= $x
then [ (.[0] + [$x]), .[1] ]
else [ .[0], (.[1] + [$x]) ]
end )
end ;
if length <= 1 then .
else strand as $s
| ($s[0] | merge( $s[1] | strand_sort))
end ;
Example: [1,3,5,2,4,6] | strand_sort
Julia
{{trans|Python}}
function mergelist(a, b) out = Vector{Int}() while !isempty(a) && !isempty(b) if a[1] < b[1] push!(out, popfirst!(a)) else push!(out, popfirst!(b)) end end append!(out, a) append!(out, b) out end function strand(a) i, s = 1, [popfirst!(a)] while i < length(a) + 1 if a[i] > s[end] append!(s, splice!(a, i)) else i += 1 end end s end strandsort(a) = (out = strand(a); while !isempty(a) out = mergelist(out, strand(a)) end; out) println(strandsort([1, 6, 3, 2, 1, 7, 5, 3]))
{{output}}
[1, 1, 2, 3, 3, 5, 6, 7]
Kotlin
{{trans|D}}
// version 1.1.2 fun <T : Comparable<T>> strandSort(l: List<T>): List<T> { fun merge(left: MutableList<T>, right: MutableList<T>): MutableList<T> { val res = mutableListOf<T>() while (!left.isEmpty() && !right.isEmpty()) { if (left[0] <= right[0]) { res.add(left[0]) left.removeAt(0) } else { res.add(right[0]) right.removeAt(0) } } res.addAll(left) res.addAll(right) return res } var list = l.toMutableList() var result = mutableListOf<T>() while (!list.isEmpty()) { val sorted = mutableListOf(list[0]) list.removeAt(0) val leftover = mutableListOf<T>() for (item in list) { if (sorted.last() <= item) sorted.add(item) else leftover.add(item) } result = merge(sorted, result) list = leftover } return result } fun main(args: Array<String>) { val l = listOf(-2, 0, -2, 5, 5, 3, -1, -3, 5, 5, 0, 2, -4, 4, 2) println(strandSort(l)) }
{{out}}
[-4, -3, -2, -2, -1, 0, 0, 2, 2, 3, 4, 5, 5, 5, 5]
Mathematica
StrandSort[ input_ ] := Module[ {results = {}, A = input},
While[Length@A > 0,
sublist = {A[[1]]}; A = A[[2;;All]];
For[i = 1, i < Length@A, i++,
If[ A[[i]] > Last@sublist, AppendTo[sublist, A[[i]]]; A = Delete[A, i];]
];
results = #[[Ordering@#]]&@Join[sublist, results];];
results ]
Example usage :
StrandSort[{2, 3, 7, 5, 1, 4, 7}]
{1, 2, 3, 4, 5, 7, 7}
MAXScript
fn strandSort arr =
(
arr = deepcopy arr
local sub = #()
local results = #()
while arr.count > 0 do
(
sub = #()
append sub (amax arr)
deleteitem arr (for i in 1 to arr.count where arr[i] == amax arr collect i)[1]
local i = 1
while i <= arr.count do
(
if arr[i] > sub[sub.count] do
(
append sub arr[i]
deleteitem arr i
)
i += 1
)
results = join sub results
)
return results
)
Output:
a = for i in 1 to 20 collect random 1 40
#(19, 26, 14, 31, 11, 33, 2, 14, 32, 28, 12, 38, 2, 37, 27, 18, 31, 24, 39, 28)
strandSort a
#(2, 2, 11, 12, 14, 14, 18, 19, 24, 26, 27, 28, 28, 31, 31, 32, 33, 37, 38, 39)
NetRexx
/* NetRexx */
options replace format comments java crossref savelog symbols binary
import java.util.List
placesList = [String -
"UK London", "US New York", "US Boston", "US Washington" -
, "UK Washington", "US Birmingham", "UK Birmingham", "UK Boston" -
]
lists = [ -
placesList -
, strandSort(String[] Arrays.copyOf(placesList, placesList.length)) -
]
loop ln = 0 to lists.length - 1
cl = lists[ln]
loop ct = 0 to cl.length - 1
say cl[ct]
end ct
say
end ln
return
method strandSort(A = String[]) public constant binary returns String[]
rl = String[A.length]
al = List strandSort(Arrays.asList(A))
al.toArray(rl)
return rl
method strandSort(Alst = List) public constant binary returns ArrayList
A = ArrayList(Alst)
result = ArrayList()
loop label A_ while A.size > 0
sublist = ArrayList()
sublist.add(A.get(0))
A.remove(0)
loop i_ = 0 while i_ < A.size - 1
if (Comparable A.get(i_)).compareTo(Comparable sublist.get(sublist.size - 1)) > 0 then do
sublist.add(A.get(i_))
A.remove(i_)
end
end i_
result = merge(result, sublist)
end A_
return result
method merge(left = List, right = List) public constant binary returns ArrayList
result = ArrayList()
loop label mx while left.size > 0 & right.size > 0
if (Comparable left.get(0)).compareTo(Comparable right.get(0)) <= 0 then do
result.add(left.get(0))
left.remove(0)
end
else do
result.add(right.get(0))
right.remove(0)
end
end mx
if left.size > 0 then do
result.addAll(left)
end
if right.size > 0 then do
result.addAll(right)
end
return result
;Output
UK London
US New York
US Boston
US Washington
UK Washington
US Birmingham
UK Birmingham
UK Boston
UK Birmingham
UK Boston
UK London
UK Washington
US Birmingham
US Boston
US New York
US Washington
Nim
proc mergeList[T](a, b: var seq[T]): seq[T] = result = @[] while a.len > 0 and b.len > 0: if a[0] < b[0]: result.add a[0] a.delete 0 else: result.add b[0] b.delete 0 result.add a result.add b proc strand[T](a: var seq[T]): seq[T] = var i = 0 result = @[a[0]] a.delete 0 while i < a.len: if a[i] > result[result.high]: result.add a[i] a.delete i else: inc i proc strandSort[T](a: seq[T]): seq[T] = var a = a result = a.strand while a.len > 0: var s = a.strand result = mergeList(result, s) var a = @[1, 6, 3, 2, 1, 7, 5, 3] echo a.strandSort
Output:
@[1, 1, 2, 3, 3, 5, 6, 7]
OCaml
{{trans|Haskell}}
let rec strand_sort (cmp : 'a -> 'a -> int) : 'a list -> 'a list = function [] -> [] | x::xs -> let rec extract_strand x = function [] -> [x], [] | x1::xs when cmp x x1 <= 0 -> let strand, rest = extract_strand x1 xs in x::strand, rest | x1::xs -> let strand, rest = extract_strand x xs in strand, x1::rest in let strand, rest = extract_strand x xs in List.merge cmp strand (strand_sort cmp rest)
usage
# strand_sort compare [170; 45; 75; -90; -802; 24; 2; 66];;
- : int list = [-802; -90; 2; 24; 45; 66; 75; 170]
PARI/GP
strandSort(v)={
my(sorted=[],unsorted=v,remaining,working);
while(#unsorted,
remaining=working=List();
listput(working, unsorted[1]);
for(i=2,#unsorted,
if(unsorted[i]<working[#working],
listput(remaining, unsorted[i])
,
listput(working, unsorted[i])
)
);
unsorted=Vec(remaining);
sorted=merge(sorted, Vec(working))
);
sorted
};
merge(u,v)={
my(ret=vector(#u+#v),i=1,j=1);
for(k=1,#ret,
if(i<=#u & (j>#v | u[i]<v[j]),
ret[k]=u[i];
i++
,
ret[k]=v[j];
j++
)
);
ret
};
Pascal
program StrandSortDemo; type TIntArray = array of integer; function merge(left: TIntArray; right: TIntArray): TIntArray; var i, j, k: integer; begin setlength(merge, length(left) + length(right)); i := low(merge); j := low(left); k := low(right); repeat if ((left[j] <= right[k]) and (j <= high(left))) or (k > high(right)) then begin merge[i] := left[j]; inc(j); end else begin merge[i] := right[k]; inc(k); end; inc(i); until i > high(merge); end; function StrandSort(s: TIntArray): TIntArray; var strand: TIntArray; i, j: integer; begin setlength(StrandSort, length(s)); setlength(strand, length(s)); i := low(s); repeat StrandSort[i] := s[i]; inc(i); until (s[i] < s[i-1]); setlength(StrandSort, i); repeat setlength(strand, 1); j := low(strand); strand[j] := s[i]; while (s[i+1] > s[i]) and (i < high(s)) do begin inc(i); inc(j); setlength(strand, length(strand) + 1); Strand[j] := s[i]; end; StrandSort := merge(StrandSort, strand); inc(i); until (i > high(s)); end; var data: TIntArray; i: integer; begin setlength(data, 8); Randomize; writeln('The data before sorting:'); for i := low(data) to high(data) do begin data[i] := Random(high(data)); write(data[i]:4); end; writeln; data := StrandSort(data); writeln('The data after sorting:'); for i := low(data) to high(data) do begin write(data[i]:4); end; writeln; end.
Perl
use 5.10.0; # for given/when sub merge { my ($x, $y) = @_; my @out; while (@$x and @$y) { given ($x->[-1] <=> $y->[-1]) { when( 1) { unshift @out, pop @$x } when(-1) { unshift @out, pop @$y } default { splice @out, 0, 0, pop(@$x), pop(@$y) } } } return @$x, @$y, @out } sub strand { my $x = shift; my @out = shift @$x // return; if (@$x) { for (-@$x .. -1) { if ($x->[$_] >= $out[-1]) { push @out, splice @$x, $_, 1 } } } return @out } sub strand_sort { my @x = @_; my @out; while (my @strand = strand(\@x)) { @out = merge(\@out, \@strand) } @out } my @a = map (int rand(100), 1 .. 10); say "Before @a"; @a = strand_sort(@a); say "After @a";
Perl 6
{{Works with|Rakudo|2018.04.01}}
(@x-in, @y-in) {
my @x = | @x-in;
my @y = | @y-in;
flat @x, @y,
reverse gather while @x and @y {
take do given @x[*-1] cmp @y[*-1] {
when More { pop @x }
when Less { pop @y }
when Same { pop(@x), pop(@y) }
}
}
}
sub strand (@x) {
my $i = 0;
my $prev = -Inf;
gather while $i < @x {
@x[$i] before $prev ?? $i++ !! take $prev = splice(@x, $i, 1)[0];
}
}
sub strand_sort (@x is copy) {
my @out;
@out M= strand(@x) while @x;
@out;
}
my @a = (^100).roll(10);
say "Before {@a}";
@a = strand_sort(@a);
say "After {@a}";
@a = <The quick brown fox jumps over the lazy dog>;
say "Before {@a}";
@a = strand_sort(@a);
say "After {@a}";
{{out}}
Before 1 20 64 72 48 75 96 55 42 74
After 1 20 42 48 55 64 72 74 75 96
Before The quick brown fox jumps over the lazy dog
After The brown dog fox jumps lazy over quick the
Phix
Copy of [[Sorting_algorithms/Strand_sort#Euphoria|Euphoria]]
function merge(sequence left, sequence right)
sequence result = {}
while length(left)>0 and length(right)>0 do
if left[$]<=right[1] then
exit
elsif right[$]<=left[1] then
return result & right & left
elsif left[1]<right[1] then
result = append(result,left[1])
left = left[2..$]
else
result = append(result,right[1])
right = right[2..$]
end if
end while
return result & left & right
end function
function strand_sort(sequence s)
integer j
sequence result = {}
while length(s)>0 do
j = length(s)
for i=1 to length(s)-1 do
if s[i]>s[i+1] then
j = i
exit
end if
end for
result = merge(result,s[1..j])
s = s[j+1..$]
end while
return result
end function
PHP
{{trans|D}} {{works with|PHP 5.3.0+}}
$lst = new SplDoublyLinkedList();
foreach (array(1,20,64,72,48,75,96,55,42,74) as $v)
$lst->push($v);
foreach (strandSort($lst) as $v)
echo "$v ";
function strandSort(SplDoublyLinkedList $lst) {
$result = new SplDoublyLinkedList();
while (!$lst->isEmpty()) {
$sorted = new SplDoublyLinkedList();
$remain = new SplDoublyLinkedList();
$sorted->push($lst->shift());
foreach ($lst as $item) {
if ($sorted->top() <= $item) {
$sorted->push($item);
} else {
$remain->push($item);
}
}
$result = _merge($sorted, $result);
$lst = $remain;
}
return $result;
}
function _merge(SplDoublyLinkedList $left, SplDoublyLinkedList $right) {
$res = new SplDoublyLinkedList();
while (!$left->isEmpty() && !$right->isEmpty()) {
if ($left->bottom() <= $right->bottom()) {
$res->push($left->shift());
} else {
$res->push($right->shift());
}
}
foreach ($left as $v) $res->push($v);
foreach ($right as $v) $res->push($v);
return $res;
}
1 20 42 48 55 64 72 74 75 96
PicoLisp
(de strandSort (Lst)
(let Res NIL # Result list
(while Lst
(let Sub (circ (car Lst)) # Build sublist as fifo
(setq
Lst (filter
'((X)
(or
(> (car Sub) X)
(nil (fifo 'Sub X)) ) )
(cdr Lst) )
Res (make
(while (or Res Sub) # Merge
(link
(if2 Res Sub
(if (>= (car Res) (cadr Sub))
(fifo 'Sub)
(pop 'Res) )
(pop 'Res)
(fifo 'Sub) ) ) ) ) ) ) )
Res ) )
Test:
: (strandSort (3 1 5 4 2))
-> (1 2 3 4 5)
: (strandSort (3 abc 1 (d e f) 5 T 4 NIL 2))
-> (NIL 1 2 3 4 5 abc (d e f) T)
PL/I
strand: procedure options (main); /* 27 Oct. 2012 */
declare A(100) fixed, used(100) bit (1), sorted fixed controlled;
declare (temp, work) fixed controlled;
declare (i, j, k, n) fixed binary;
n = hbound(A, 1);
used = '1'b;
A = random()*99;
put edit (A) (f(3));
do while (allocation(sorted) < n);
call fetch (A, work);
call move (temp, work);
call merge(sorted, temp);
/* Merges elements in SORTED with elements in TEMP. */
end;
/* Transfer the sorted elements to A. */
do i = 1 to allocation(sorted);
A(i) = sorted; free sorted;
end;
/* Print the sorted values. */
put skip list ('The sorted values are:');
put skip edit (A) (f(3));
/* Merges elements of SORTED with elements of TEMP and places */
/* the result in SORTED. */
/* Elements in SORTED and TEMP are in forward order. */
merge: procedure (sorted, temp);
declare (sorted, temp) fixed controlled;
declare work fixed controlled;
declare (j_ok, k_ok) bit (1);
do until ((k_ok | j_ok) = '0'b);
k_ok = allocation(sorted) > 0;
j_ok = allocation(temp) > 0;
if k_ok & j_ok then
do;
if sorted <= temp then
do; allocate work; work = sorted; free sorted; end;
else
do; allocate work; work = temp; free temp; end;
end;
else
if allocation(temp) = 0 then
/* temp is empty; copy remainder of sorted into work */
do while (allocation(sorted) > 0);
allocate work; work = sorted; free sorted;
end;
else
/* sorted is empty; copy remainder of temp onto work */
do while (allocation(temp) > 0);
allocate work; work = temp; free temp;
end;
end;
call move (sorted, work); /* Move the values to SORTED. */
end merge;
/* Collect a thread of ascending values from aray A, and stack them in temp. */
/* Note: the values in temp are in reverse order. */
fetch: procedure (A, temp);
declare A(*) fixed, temp controlled fixed;
declare i fixed binary;
do i = 1 to hbound(A,1);
if used(i) then
do; allocate temp; temp = A(i); used(i) = '0'b; go to found; end;
end;
found:
do i = i+1 to hbound(A,1);
if (temp <= A(i)) & used(i) then
do; allocate temp; temp = A(i); used(i) = '0'b; end;
end;
end fetch;
/* Copy the stack at TEMP to the stack at SORTED. */
/* In TEMP, elements are in reverse order; */
/* in SORTED, elements are in forward order. */
move: procedure (sorted, temp);
declare (sorted, temp) fixed controlled;
do while (allocation(sorted) > 0); free sorted; end;
do while (allocation (temp) > 0);
allocate sorted; sorted = temp; free temp;
end;
end move;
end strand;
Generated data:
43 5 79 16 90 48 29 73 29 19 77 59 49 2 54 35 39 71 25 76 34 48 31 91 28 13 23 70 27 59 96 7 63 82 59 81 28 96 34 43
81 98 21 47 72 57 45 64 94 51 18 11 65 12 61 97 13 84 95 89 43 8 14 31 58 68 58 39 59 26 72 38 26 85 30 89 42 90 29 11
14 63 97 60 1 17 45 42 62 29 45 15 69 11 29 25 11 48 92 3
Results:
The sorted values are:
1 2 3 5 7 8 11 11 11 11 12 13 13 14 14 15 16 17 18 19 21 23 25 25 26 26 27 28 28 29 29 29 29 29 30 31 31 34 34 35
38 39 39 42 42 43 43 43 45 45 45 47 48 48 48 49 51 54 57 58 58 59 59 59 59 60 61 62 63 63 64 65 68 69 70 71 72 72 73 76
77 79 81 81 82 84 85 89 89 90 90 91 92 94 95 96 96 97 97 98
PureBasic
Procedure strandSort(List a())
Protected NewList subList()
Protected NewList results()
While ListSize(a()) > 0
ClearList(subList())
AddElement(subList())
FirstElement(a())
subList() = a()
DeleteElement(a())
ForEach a()
If a() >= subList()
AddElement(subList())
subList() = a()
DeleteElement(a())
EndIf
Next
;merge lists
FirstElement(subList())
If Not FirstElement(results())
;copy all of sublist() to results()
MergeLists(subList(), results(), #PB_List_Last)
Else
Repeat
If subList() < results()
InsertElement(results())
results() = subList()
DeleteElement(subList())
If Not NextElement(subList())
Break
EndIf
ElseIf Not NextElement(results())
;add remainder of sublist() to end of results()
MergeLists(subList(), results(), #PB_List_Last)
Break
EndIf
ForEver
EndIf
Wend
CopyList(results(), a())
EndProcedure
Procedure.s listContents(List a())
Protected output.s
PushListPosition(a())
ForEach a()
output + Str(a()) + ","
Next
PopListPosition(a())
ProcedureReturn Left(output, Len(output) - 1)
EndProcedure
Procedure setupList(List a())
ClearList(a())
Protected elementCount, i
elementCount = Random(5) + 10
For i = 1 To elementCount
AddElement(a())
a() = Random(10) - 5
Next
EndProcedure
If OpenConsole()
NewList sample()
Define i
For i = 1 To 3
setupList(sample())
PrintN("List " + Str(i) + ":")
PrintN(" Before: " + listContents(sample()))
strandSort(sample())
PrintN(" After : " + listContents(sample()))
PrintN("")
Next
Print(#CRLF$ + #CRLF$ + "Press ENTER to exit"): Input()
CloseConsole()
EndIf
Sample output:
List 1:
Before: 3,-2,-4,4,-1,-3,-2,-2,2,2,0
After : -4,-3,-2,-2,-2,-1,0,2,2,3,4
List 2:
Before: -4,4,3,-2,3,-2,5,0,-1,0,5,1
After : -4,-2,-2,-1,0,0,1,3,3,4,5,5
List 3:
Before: -2,0,-2,5,5,3,-1,-3,5,5,0,2,-4,4,2
After : -4,-3,-2,-2,-1,0,0,2,2,3,4,5,5,5,5
Python
def merge_list(a, b): out = [] while len(a) and len(b): if a[0] < b[0]: out.append(a.pop(0)) else: out.append(b.pop(0)) out += a out += b return out def strand(a): i, s = 0, [a.pop(0)] while i < len(a): if a[i] > s[-1]: s.append(a.pop(i)) else: i += 1 return s def strand_sort(a): out = strand(a) while len(a): out = merge_list(out, strand(a)) return out print strand_sort([1, 6, 3, 2, 1, 7, 5, 3])
Output:
## Racket
```racket
#lang racket
(require mzlib/list)
(define (merge xs ys) (merge-sorted-lists xs ys <=))
(define (strand-sort xs)
(let loop ([xs xs] [ys '[]])
(cond [(empty? xs) ys]
[else (define-values (sorted unsorted) (extract-strand xs))
(loop unsorted (merge sorted ys))])))
(define (extract-strand xs)
(for/fold ([strand '()] [unsorted '[]]) ([x xs])
(if (or (empty? strand) (< x (first strand)))
(values (cons x strand) unsorted)
(values strand (cons x unsorted)))))
(strand-sort (build-list 10 (λ(_) (random 15))))
REXX
This REXX program was written to generate a specified amount of random numbers as well as allowing a pre-pended list of numbers).
It can handle integers, floating point numbers, exponentiated numbers, and/or character strings.
/*REXX program sorts a random list of words (or numbers) using the strand sort algorithm*/
parse arg size minv maxv old /*obtain optional arguments from the CL*/
if size=='' | size=="," then size=20 /*Not specified? Then use the default.*/
if minv=='' | minv=="," then minv= 0 /*Not specified? Then use the default.*/
if maxv=='' | maxv=="," then maxv=size /*Not specified? Then use the default.*/
do i=1 for size /*generate a list of random numbers. */
old=old random(0,maxv-minv)+minv /*append a random number to a list. */
end /*i*/
old=space(old) /*elide extraneous blanks from the list*/
say center('unsorted list', length(old), "─"); say old
new=strand_sort(old) /*sort the list of the random numbers. */
say; say center('sorted list' , length(new), "─"); say new
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
strand_sort: procedure; parse arg x; y=
do while words(x)\==0; w=words(x)
do j=1 for w-1 /*anything out of order?*/
if word(x,j)>word(x,j+1) then do; w=j; leave; end
end /*j*/
y=merge(y,subword(x,1,w)); x=subword(x,w+1)
end /*while*/
return y
/*──────────────────────────────────────────────────────────────────────────────────────*/
merge: procedure; parse arg a.1,a.2; p=
do forever; w1=words(a.1); w2=words(a.2) /*do while 2 lists exist*/
if w1==0 | if w2==0 then leave /*Any list empty? Stop.*/
if word(a.1,w1) <= word(a.2,1) then leave /*lists are now sorted? */
if word(a.2,w2) <= word(a.1,1) then return space(p a.2 a.1)
#=1+(word(a.1,1) >= word(a.2,1)); p=p word(a.#,1); a.#=subword(a.#,2)
end /*forever*/
return space(p a.1 a.2)
'''output''' when using the input of: 25 -9 30 1000 2000 3000
────────────────────────────────unsorted list────────────────────────────────
1000 2000 3000 9 0 3 -8 17 8 -2 4 0 -3 19 -1 3 1 8 27 14 20 2 -6 23 1 -8 -4 4
─────────────────────────────────sorted list─────────────────────────────────
-8 -8 -6 -4 -3 -2 -1 0 0 1 1 2 3 3 4 4 8 8 9 14 17 19 20 23 27 1000 2000 3000
The REXX program can also sort words as well as numbers.
'''output''' when using the input of: 24 -9 100 66 66 8.8 carp Carp
──────────────────────────────────────unsorted list───────────────────────────────────────
66 66 8.8 carp Carp 20 77 88 9 39 -5 10 12 80 87 26 61 87 94 73 27 49 35 95 81 76 40 13 72
───────────────────────────────────────sorted list────────────────────────────────────────
-5 8.8 9 10 12 13 20 26 27 35 39 40 49 61 66 66 72 73 76 77 80 81 87 87 88 94 95 Carp carp
Note that an ASCII computer will sort words differently than an EBCDIC machine.
The order of sorting on an ASCII machine is: numbers, upperCase, lowerCase
The order of sorting on an EBCDIC machine is: lowerCase, upperCase, numbers
Ring
# Project : Sorting algorithms/Strand sort
test = [-2,0,-2,5,5,3,-1,-3,5,5,0,2,-4,4,2]
results = []
resultsend = []
see "before sort:" + nl
showarray(test)
test = strandsort(test)
see "after sort:" + nl
showarray(test)
func strandsort(a)
while len(a) > 0
sublist = []
add(sublist,a[1])
del(a,1)
for i = 1 to len(a)
if a[i] > sublist[len(sublist)]
add(sublist,a[i])
del(a,i)
ok
next
for n = 1 to len(sublist)
add(results,sublist[n])
next
for n = 1 to len(results)
for m = n + 1 to len(results)
if results[m] < results[n]
temp = results[m]
results[m] = results[n]
results[n] = temp
ok
next
next
end
return results
func showarray(vect)
svect = ""
for n = 1 to len(vect)
svect = svect + vect[n] + " "
next
svect = left(svect, len(svect) - 1)
see svect + nl
Output:
before sort:
-2 0 -2 5 5 3 -1 -3 5 5 0 2 -4 4 2
after sort:
-4 -3 -2 -2 -1 0 0 2 2 3 4 5 5 5 5
Ruby
class Array def strandsort a = dup result = [] until a.empty? v = a.first sublist, a = a.partition{|val| v=val if v<=val} # In case of v>val, it becomes nil. result.each_index do |idx| break if sublist.empty? result.insert(idx, sublist.shift) if sublist.first < result[idx] end result += sublist end result end def strandsort! replace(strandsort) end end p [1, 6, 3, 2, 1, 7, 5, 3].strandsort
{{out}}
[1, 1, 2, 3, 3, 5, 6, 7]
Sidef
{{trans|Perl}}
func merge(x, y) { var out = []; while (x && y) { given (x[-1] <=> y[-1]) { when ( 1) { out.prepend(x.pop) } when (-1) { out.prepend(y.pop) } default { out.prepend(x.pop, y.pop) } } } x + y + out; } func strand(x) { x || return []; var out = [x.shift]; if (x.len) { for i in (-x.len .. -1) { if (x[i] >= out[-1]) { out.append(x.pop_at(i)); } } } return out; } func strand_sort(x) { var out = []; while (var strd = strand(x)) { out = merge(out, strd); } return out; } var a = 10.of { 100.irand }; say "Before: #{a}"; say "After: #{strand_sort(a)}";
{{out}}
Before: 24 62 29 95 11 21 46 3 23 20
After: 3 11 20 21 23 24 29 46 62 95
Tcl
proc merge {listVar toMerge} { upvar 1 $listVar v set i [set j 0] set out {} while {$i<[llength $v] && $j<[llength $toMerge]} { if {[set a [lindex $v $i]] < [set b [lindex $toMerge $j]]} { lappend out $a incr i } else { lappend out $b incr j } } # Done the merge, but will be one source with something left # This will handle all that by doing a merge of the remnants onto the end set v [concat $out [lrange $v $i end] [lrange $toMerge $j end]] return } proc strandSort A { set results {} while {[llength $A]} { set sublist [lrange $A 0 0] # We build a list of items that weren't filtered rather than removing "in place" # because this fits better with the way Tcl values work (the underlying data # structure is an array, not a linked list). set newA {} foreach a [lrange $A 1 end] { if {$a > [lindex $sublist end]} { lappend sublist $a } else { lappend newA $a } } set A $newA merge results $sublist } return $results } puts [strandSort {3 1 5 4 2}]
Ursala
strand_sort "r" = # parameterized by a relational predicate "r"
@NiX -+
:-0 ~&B^?a\~&Y@a "r"?abh/~&alh2faltPrXPRC ~&arh2falrtPXPRC,
~&r->l ^|rlPlCrrPX/~& @hNCNXtX ~&r->lbx "r"?rllPXh/~&llPrhPlrPCXrtPX ~&rhPllPClrPXrtPX+-
demonstration code:
#cast %nL
x = (strand_sort nat-nleq) <3,1,5,4,2>
output:
<1,2,3,4,5>
zkl
fcn strandSort(A){ //--> new list, A is cleared, should add A=A.copy()
sublist:=List.createLong(A.len()); results:=List.createLong(A.len());
while(A){
sublist.clear(A.pop(0));
foreach i in (A.len() - 1){
if(A[i]>sublist[-1]) sublist.append(A.pop(i));
}
results.merge(sublist);
}
results
}
The createLong list method creates a new list with pre-allocated space
strandSort(L(3,1,5,4,2)).println();
strandSort("azbfe".split("")).println();
{{out}}
L(1,2,3,4,5)
L("a","b","e","f","z")
{{omit from|GUISS}}