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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 unsorted:-2 0 -2 5 5 3 -1 -3 5 5 0 2 -4 4 2 Sorted:-4 -3 -2 -2 -1 0 0 2 2 3 4 5 5 5 5

```

## 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->tail)  l->tail->next = e;
l->tail = e;
}

if (e) {
e->next = 0;
}
return e;
}

void join(slist *a, slist *b) {
a->tail = b->tail;
}

void merge(slist *a, slist *b) {
slist r = {0};

join(&r, a->head ? a : b);
*a = r;
}

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) {
push((!strand.head || e->v >= strand.tail->v) ? &strand : &rem, e);

merge(&res, &strand);
}

// list to array
}

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;
}
```

outoutbefore 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

```

## 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_.
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)
math(EXPR la "\${la} + 1")
endforeach(e)
set(lb 0)
foreach(e \${accept})
math(EXPR lb "\${lb} + 1")
set(accept\${lb} \${e})
endforeach(e)

set(ia 1)
set(ib 1)
while(NOT ia GREATER \${la})         # Iterate elements of _answer_.
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_.
math(EXPR ib "\${ib} + 1")
else()
break()
endif()
endwhile()
math(EXPR ia "\${ia} + 1")
endwhile()
while(NOT ib GREATER \${lb})         # Take rest of _accept_.
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)

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(5 8 6 0 6 8 4 7 0 7 1 5 3 3 6) (0 0 1 3 3 4 5 5 6 6 6 7 7 8 8)

```

## D

```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"

int
}

if len(s) == 0 {
return nil
}
}

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)
}

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
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]

```

```-- 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;

public class Strand{
// note: the input list is destroyed
public static <E extends Comparable<? super E>>
if(list.size() <= 1) return list;

while(list.size() > 0){
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){
it.remove();
}
}
result = merge(sorted, result);
}
return result;
}

private static <E extends Comparable<? super 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)
else
}
return result;
}

public static void main(String[] args){
}
}
```

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]) {
left.removeAt(0)
}
else {
right.removeAt(0)
}
}
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)
else
}
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()
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
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
left.remove(0)
end
else do
right.remove(0)
end
end mx
if left.size > 0 then do
end
if right.size > 0 then do
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]:
a.delete 0
else:
b.delete 0

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]:
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

```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 ";

while (!\$lst->isEmpty()) {
\$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;
}

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
(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())
FirstElement(a())
subList() = a()
DeleteElement(a())
ForEach a()
If a() >= 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
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:[1, 1, 2, 3, 3, 5, 6, 7]

```

## 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 = []
del(a,1)
for i = 1 to len(a)
if a[i] > sublist[len(sublist)]
del(a,i)
ok
next
for n = 1 to len(sublist)
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}}