Sorting algorithms/Cycle sort

Sorting algorithms/Cycle sort is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.
 This page uses content from Wikipedia. The original article was at Cycle_sort. The list of authors can be seen in the page history. As with Rosetta Code, the text of Wikipedia is available under the GNU FDL. (See links for details on variance)

From the the Wikipedia entry on cycle sorting:

Cycle sort is an in-place, unstable sorting algorithm, a comparison sort that is theoretically optimal in terms of the total number of writes to the original array, unlike any other in-place sorting algorithm.
It is based on the idea that the permutation to be sorted can be factored into cycles, which can individually be rotated to give a sorted result.
Unlike nearly every other sort, items are never written elsewhere in the array simply to push them out of the way of the action.
Each value is either written zero times, if it's already in its correct position, or written one time to its correct position.
This matches the minimal number of overwrites required for a completed in-place sort.
Minimizing the number of writes is useful when making writes to some huge data set is very expensive, such as with EEPROMs like Flash memory where each write reduces the lifespan of the memory.
• Youtube Visualization and audibilization of Cycle Sort algorithm.

360 Assembly

Translation of: NetRexx

The program uses ASM structured macros and two ASSIST macros to keep the code as short as possible.

*        Cycle sort                26/06/2016CYCLESRT CSECT         USING  CYCLESRT,R13       base register         B      72(R15)            skip savearea         DC     17F'0'             savearea         STM    R14,R12,12(R13)    prolog         ST     R13,4(R15)         "         ST     R15,8(R13)         "          LR     R13,R15            "         LA     RJ,1               jcycle=1         L      R2,N               n         BCTR   R2,0               n-1         ST     R2,NM1             nm1=n-1         DO WHILE=(C,RJ,LE,NM1)    do jcycle=1 to n-1         LR     R1,RJ              jcycle         SLA    R1,2               .         L      RM,A-4(R1)         item=a(jcycle)         LR     RK,RJ              kpos=jcycle       /*find{*/         LA     RI,1(RJ)           i=jcycle+1         DO WHILE=(C,RI,LE,N)      do i=jcycle+1 to n         LR     R1,RI                i         SLA    R1,2                 .         L      R2,A-4(R1)           a(i)         IF     CR,R2,LT,RM THEN     if a(i)<item then         LA     RK,1(RK)               kpos=kpos+1         ENDIF  ,                    end if         LA     RI,1(RI)             i=i+1         ENDDO  ,                  end do            /*}*/         IF     CR,RK,NE,RJ THEN   if kpos^=jcycle then    ======         LR     R1,RK              kpos              /*put{*/         SLA    R1,2               .         LA     R2,A-4(R1)         @a(kpos)         DO WHILE=(C,RM,EQ,0(R2))  do while item=a(kpos)         LA     RK,1(RK)             kpos=kpos+1         LA     R2,4(R2)             @a(kpos)[email protected]/* <![CDATA[ */!function(t,e,r,n,c,a,p){try{t=document.currentScript||function(){for(t=document.getElementsByTagName('script'),e=t.length;e--;)if(t[e].getAttribute('data-cfhash'))return t[e]}();if(t&&(c=t.previousSibling)){p=t.parentNode;if(a=c.getAttribute('data-cfemail')){for(e='',r='0x'+a.substr(0,2)|0,n=2;a.length-n;n+=2)e+='%'+('0'+('0x'+a.substr(n,2)^r).toString(16)).slice(-2);p.replaceChild(document.createTextNode(decodeURIComponent(e)),c)}p.removeChild(t)}}catch(u){}}()/* ]]> */(kpos)+4         ENDDO  ,                  end do         LR     R1,RK              kpos         SLA    R1,2               .         LA     R2,A-4(R1)         @a(kpos)         L      RT,0(R2)           temp=a(kpos)         ST     RM,0(R2)           a(kpos)=item         LR     RM,RT              item=temp         L      R2,WRITES          writes         LA     R2,1(R2)           writes+1         ST     R2,WRITES          writes=writes+1   /*}*/         DO WHILE=(CR,RK,NE,RJ)    do while(kpos^=jcycle)   -----         LR     RK,RJ                kpos=jcycle       /*find{*/         LA     RI,1(RJ)             i=jcycle+1         DO WHILE=(C,RI,LE,N)        do i=jcycle+1 to n         LR     R1,RI                  i         SLA    R1,2                   .         L      R2,A-4(R1)             a(i)         IF     CR,R2,LT,RM THEN       if a(i)<item then         LA     RK,1(RK)                 kpos=kpos+1         ENDIF  ,                       end if         LA     RI,1(RI)               i=i+1         ENDDO  ,                    end do            /*}*/         LR     R1,RK                kpos              /*put{*/         SLA    R1,2                 .         LA     R2,A-4(R1)           @a(kpos)         DO WHILE=(C,RM,EQ,0(R2))    do while item=a(kpos)         LA     RK,1(RK)               kpos=kpos+1         LA     R2,4(R2)               @a(kpos)[email protected]/* <![CDATA[ */!function(t,e,r,n,c,a,p){try{t=document.currentScript||function(){for(t=document.getElementsByTagName('script'),e=t.length;e--;)if(t[e].getAttribute('data-cfhash'))return t[e]}();if(t&&(c=t.previousSibling)){p=t.parentNode;if(a=c.getAttribute('data-cfemail')){for(e='',r='0x'+a.substr(0,2)|0,n=2;a.length-n;n+=2)e+='%'+('0'+('0x'+a.substr(n,2)^r).toString(16)).slice(-2);p.replaceChild(document.createTextNode(decodeURIComponent(e)),c)}p.removeChild(t)}}catch(u){}}()/* ]]> */(kpos)+4         ENDDO  ,                    end do         LR     R1,RK                kpos         SLA    R1,2                 .         LA     R2,A-4(R1)           @a(kpos)         L      RT,0(R2)             temp=a(kpos)         ST     RM,0(R2)             a(kpos)=item         LR     RM,RT                item=temp         L      R2,WRITES            writes         LA     R2,1(R2)             writes+1         ST     R2,WRITES            writes=writes+1   /*}*/         ENDDO  ,                  end while   ------------------         ENDIF  ,                  end if   =====================         LA     RJ,1(RJ)           jcycle=jcycle+1         ENDDO  ,                  end do jcycle         LA     R3,PG              pgi=0         LA     RI,1               i=1         DO     WHILE=(C,RI,LE,N)  do i=1 to n         LR     R1,RI                i         SLA    R1,2                 .         L      R2,A-4(R1)           a(i)         XDECO  R2,XDEC              edit a(i)         MVC    0(4,R3),XDEC+8       output a(i)         LA     R3,4(R3)             pgi=pgi+4         LA     RI,1(RI)             i=i+1         ENDDO  ,                  end do         XPRNT  PG,L'PG            print buffer         L      R1,WRITES          writes         XDECO  R1,XDEC            edit writes         MVC    XDEC(7),=CL7'writes='         XPRNT  XDEC,L'XDEC        print buffer         L      R13,4(0,R13)       epilog          LM     R14,R12,12(R13)    "         XR     R15,R15            "         BR     R14                exitA     DC F'4',F'65',F'2',F'-31',F'0',F'99',F'2',F'83',F'782',F'1'      DC F'45',F'82',F'69',F'82',F'104',F'58',F'88',F'112',F'89',F'74'N        DC     A((N-A)/L'A)       number of items of aNM1      DS     F                  n-1PG       DC     CL80' '            bufferXDEC     DS     CL12               temp for xdecoWRITES   DC     F'0'               number of writes         YREGSRI       EQU    6                  iRJ       EQU    7                  jcycleRK       EQU    8                  kposRT       EQU    9                  tempRM       EQU    10                 item         END    CYCLESRT
Output:
 -31   0   1   2   2   4  45  58  65  69  74  82  82  83  88  89  99 104 112 782


C

Translation of: NetRexx
 #include <stdio.h>#include <stdlib.h> int cycleSort(int * list, size_t l_len);void show_array(int * array, size_t a_len); /* * Sort an array in place and return the number of writes. */int cycleSort(int * list, size_t l_len){  int writes = 0;   /* Loop through the array to find cycles to rotate. */  for (int cycleStart = 0; cycleStart < l_len - 1; ++cycleStart)  {    int item = list[cycleStart];    int swap_tmp;     /* Find where to put the item. */    int pos = cycleStart;    for (int i = cycleStart + 1; i < l_len; ++i)    {      if (list[i] < item)      {        ++pos;      }    }     /* If the item is already there, this is not a cycle. */    if (pos == cycleStart)    {      continue;    }     /* Otherwise, put the item there or right after any duplicates. */    while (item == list[pos])    {      ++pos;    }    swap_tmp = list[pos];    list[pos] = item;    item = swap_tmp;    ++writes;     /* Rotate the rest of the cycle. */    while (pos != cycleStart)    {      /* Find where to put the item. */      pos = cycleStart;      for (int i = cycleStart + 1; i < l_len; ++i)      {        if (list[i] < item)        {          ++pos;        }      }       /* Put the item there or right after any duplicates. */      while (item == list[pos])      {        ++pos;      }      swap_tmp = list[pos];      list[pos] = item;      item = swap_tmp;      ++writes;    }  }   return writes;} int main(int argc, char ** argv){  int arr[] = { 0, 1, 2, 2, 2, 2, 1, 9, 3, 5, 5, 8, 4, 7, 0, 6, };  int arr_k = sizeof(arr) / sizeof(arr[0]);  int writes;   show_array(arr, arr_k);  writes = cycleSort(arr, arr_k);  show_array(arr, arr_k);  printf("writes: %d\n", writes);   return 0;} void show_array(int * array, size_t a_len){  for (int ix = 0; ix < a_len; ++ix)  {    printf("%d ", array[ix]);  }  putchar('\n');   return;}
Output:
0 1 2 2 2 2 1 9 3 5 5 8 4 7 0 6
0 0 1 1 2 2 2 2 3 4 5 5 6 7 8 9
writes: 10


C++

Based on example code on Wikipedia

 #include <time.h>#include <iostream>#include <vector> using namespace std; class cSort{public:    void doIt( vector<unsigned> s )    {	sq = s; display(); c_sort();	cout << "writes: " << wr << endl; display();     }private:    void display()    {	copy( sq.begin(), sq.end(), ostream_iterator<unsigned>( std::cout, " " ) );	cout << endl;    }    void c_sort()    {	wr = 0;	unsigned it, p, vlen = static_cast<unsigned>( sq.size() ); 	for( unsigned c = 0; c < vlen - 1; c++ )	{	    it = sq[c];	    p = c;	    for( unsigned d = c + 1; d < vlen; d++ )		if( sq[d] < it ) p++; 	    if( c == p ) continue; 	    doSwap( p, it ); 	    while( c != p )	    {		p = c;		for( unsigned e = c + 1; e < vlen; e++ )		    if( sq[e] < it ) p++; 		doSwap( p, it );	    }	}    }    void doSwap( unsigned& p, unsigned& it )    {	while( sq[p] == it ) p++;	swap( it, sq[p] );	wr++;    }    vector<unsigned> sq;    unsigned wr;}; int main(int argc, char ** argv){    srand( static_cast<unsigned>( time( NULL ) ) );    vector<unsigned> s;    for( int x = 0; x < 20; x++ )	s.push_back( rand() % 100 + 21 );     cSort c; c.doIt( s );    return 0;}
Output:
38 119 38 33 33 28 24 101 108 120 99 59 69 24 117 22 90 94 78 75
writes: 19
22 24 24 28 33 33 38 38 59 69 75 78 90 94 99 101 108 117 119 120


D

This version doesn't use Phobos algorithms beside 'swap'. Algorithms can be used to find where to put the item1 and elsewhere.

Translation of: Python
import std.stdio, std.algorithm; /// Sort an array in place and return the number of writes.uint cycleSort(T)(T[] data) pure nothrow @safe @nogc {    typeof(return) nWrites = 0;     // Loop through the data to find cycles to rotate.    foreach (immutable cycleStart, item1; data) {        // Find where to put the item1.        size_t pos = cycleStart;        foreach (item2; data[cycleStart + 1 .. $]) if (item2 < item1) pos++; // If the item1 is already there, this is not a cycle. if (pos == cycleStart) continue; // Otherwise, put the item1 there or right after any duplicates. while (item1 == data[pos]) pos++; data[pos].swap(item1); nWrites++; // Rotate the rest of the cycle. while (pos != cycleStart) { // Find where to put the item1. pos = cycleStart; foreach (item2; data[cycleStart + 1 ..$])                if (item2 < item1)                    pos++;             // Put the item1 there or right after any duplicates.            while (item1 == data[pos])                pos++;            data[pos].swap(item1);            nWrites++;        }    }     return nWrites;} void main() {    immutable x = [0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6];    auto xs = x.dup;    immutable nWrites = xs.cycleSort;     if (!xs.isSorted) {        "Wrong order!".writeln;    } else {        writeln(x, "\nIs correctly sorted using cycleSort to:");        writefln("%s\nusing %d writes.", xs, nWrites);    }}
Output:
[0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]
Is correctly sorted using cycleSort to:
[0, 0, 1, 1, 2, 2, 2, 2, 3.5, 4, 5, 6, 7, 8, 9]
using 10 writes.

Elixir

Translation of: Ruby
defmodule Sort do  def cycleSort(list) do    tuple = List.to_tuple(list)    # Loop through the array to find cycles to rotate.    {data,writes} = Enum.reduce(0 .. tuple_size(tuple)-2, {tuple,0}, fn cycleStart,{data,writes} ->      item = elem(data, cycleStart)      pos = find_pos(data, cycleStart, item)      if pos == cycleStart do        # If the item is already there, this is not a cycle.        {data, writes}      else        # Otherwise, put the item there or right after any duplicates.        {data, item} = swap(data, pos, item)        rotate(data, cycleStart, item, writes+1)      end    end)    {Tuple.to_list(data), writes}  end   # Rotate the rest of the cycle.  defp rotate(data, cycleStart, item, writes) do    pos = find_pos(data, cycleStart, item)    {data, item} = swap(data, pos, item)    if pos==cycleStart, do: {data, writes+1},                      else: rotate(data, cycleStart, item, writes+1)  end   # Find where to put the item.  defp find_pos(data, cycleStart, item) do    cycleStart + Enum.count(cycleStart+1..tuple_size(data)-1, &elem(data, &1) < item)  end   # Put the item there or right after any duplicates.  defp swap(data, pos, item) when elem(data, pos)==item, do: swap(data, pos+1, item)  defp swap(data, pos, item) do    {put_elem(data, pos, item), elem(data, pos)}  endend IO.inspect a = [0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]{b, writes} = Sort.cycleSort(a)IO.puts "writes : #{writes}"IO.inspect b
Output:
[0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]
writes : 10
[0, 0, 1, 1, 2, 2, 2, 2, 3.5, 4, 5, 6, 7, 8, 9]


FreeBASIC

Uses algorithm in Wikipedia article:

' FB 1.05.0 Win64 ' sort an array in place and return the number of writesFunction cycleSort(array() As Integer) As Integer  Dim length As Integer = UBound(array) - LBound(array) + 1  If Length = 0 Then Return 0  Dim As Integer item, position, writes = 0   ' loop through the array to find cycles to rotate  For cycleStart As Integer = LBound(array) To UBound(array) - 1    item = array(cycleStart)     ' find where to put the item    position = cycleStart    For i As Integer = cycleStart + 1 To UBound(array)      If array(i) < item Then position += 1    Next i     ' If the item is already there, this is not a cycle    If position = cycleStart Then Continue For     ' Otherwise, put the item there or right after any duplicates    While item = array(position)      position += 1    Wend    Swap array(position), item    writes += 1     'rotate the rest of the cycle    While position <> cycleStart      ' Find where to put the item      position = cycleStart      For i As Integer = cycleStart + 1 To UBound(array)        If array(i) < item Then position += 1      Next i       ' Put the item there or right after any duplicates      While item = array(position)        position += 1      Wend      Swap array(position), item      writes +=1    Wend  Next cycleStart   Return writesEnd Function Sub printArray(array() As Integer)  For i As Integer = LBound(array) To UBound(array)    Print Str(array(i)); " ";  Next  PrintEnd Sub Dim array(1 To 16) As Integer = {0, 1, 2, 2, 2, 2, 1, 9, 3, 5, 5, 8, 4, 7, 0, 6}printArray(array())Dim writes As Integer = cycleSort(array())Print "After sorting with"; writes; " writes :"printArray(array())PrintDim array2(1 To 20) As Integer = {38, 119, 38, 33, 33, 28, 24, 101, 108, 120, 99, 59, 69, 24, 117, 22, 90, 94, 78, 75}printArray(array2())writes = cycleSort(array2())Print "After sorting with"; writes; " writes :"printArray(array2())Print Print "Press any key to quit"Sleep
Output:
0 1 2 2 2 2 1 9 3 5 5 8 4 7 0 6
After sorting with 10 writes :
0 0 1 1 2 2 2 2 3 4 5 5 6 7 8 9

38 119 38 33 33 28 24 101 108 120 99 59 69 24 117 22 90 94 78 75
After sorting with 19 writes :
22 24 24 28 33 33 38 38 59 69 75 78 90 94 99 101 108 117 119 120


Go

This implementation was translated from the example code on Wikipedia.

package main import (	"fmt"	"math/rand"	"time") func cyclesort(ints []int) int {	writes := 0 	for cyclestart := 0; cyclestart < len(ints)-1; cyclestart++ {		item := ints[cyclestart] 		pos := cyclestart 		for i := cyclestart + 1; i < len(ints); i++ {			if ints[i] < item {				pos++			}		} 		if pos == cyclestart {			continue		} 		for item == ints[pos] {			pos++		} 		ints[pos], item = item, ints[pos] 		writes++ 		for pos != cyclestart {			pos = cyclestart			for i := cyclestart + 1; i < len(ints); i++ {				if ints[i] < item {					pos++				}			} 			for item == ints[pos] {				pos++			} 			ints[pos], item = item, ints[pos]			writes++		}	} 	return writes} func main() {	rand.Seed(time.Now().Unix()) 	ints := rand.Perm(10) 	fmt.Println(ints)	fmt.Printf("writes %d\n", cyclesort(ints))	fmt.Println(ints)}
Output:
[1 9 3 5 8 4 7 0 6 2]
writes 10
[0 1 2 3 4 5 6 7 8 9]


Note: output may be different due to the random numbers used.

J

J's sort is natively a single write sort, but it assigns the whole array at once. It would be trivial do the writes one at a time, and to avoid updating values which are not changed:

noncyc=:3 :0  writes=. 0  for_item. /:~y do.    if. item ~: item_index{y do.      writes=. writes+1      y=.item item_index} y    end.  end.  smoutput (":writes),' writes'  y )
Example use:
   noncyc 9 8 15 17 4 0 1 2 17 9 3 12 11 12 19 15 3 9 16 917 writes0 1 2 3 3 4 8 9 9 9 9 11 12 12 15 15 16 17 17 19

Meanwhile, if we just wanted the "value at a time swapping" mechanism, an idiomatic approach might look something like this:

cyc0=:3 :0  c=. (#~ 1 < #@>)C./:/: y  writes=. 0  for_box. c do.    inds=. >box    v=. ({:inds) { y    for_ind. inds do.      writes=. writes+1      t=. ind{ y      y=. v ind} y      v=. t    end.  end.  smoutput (":writes),' writes'  y)
Example use:
   cyc0 9 8 15 17 4 0 1 2 17 9 3 12 11 12 19 15 3 9 16 918 writes0 1 2 3 3 4 8 9 9 9 9 11 12 12 15 15 16 17 17 19

This gives us an extra write, because we're using a generic cycle abstraction.

Also that's still a bit different from the wikipedia algorithm. We might model the wikipedia algorithm like this:

cyc1=:3 :0  writes=. 0  for_index. i.(#y)-1 do.    item=. index{y    adj=. item+/ .>(1+index)}.y    if. 0<adj do.      pos=. index+adj      while. item=pos{y do. pos=.pos+1 end.      writes=. writes+1      t=. pos{y      y=. item pos} y      item=. t      while. pos ~: index do.        pos=. index+item+/ .>(1+index)}.y        while. item=pos{y do. pos=.pos+1 end.        writes=. writes+1        t=. pos{y        y=. item pos} y        item=. t      end.    end.  end.  smoutput (":writes),' writes'  y)
Example use:
   cyc1 9 8 15 17 4 0 1 2 17 9 3 12 11 12 19 15 3 9 16 917 writes0 1 2 3 3 4 8 9 9 9 9 11 12 12 15 15 16 17 17 19

Note that we've saved a write in this case, by following the wikipedia algorithm.

Java

import java.util.Arrays; public class CycleSort {     public static void main(String[] args) {        int[] arr = {5, 0, 1, 2, 2, 3, 5, 1, 1, 0, 5, 6, 9, 8, 0, 1};         System.out.println(Arrays.toString(arr));         int writes = cycleSort(arr);        System.out.println(Arrays.toString(arr));        System.out.println("writes: " + writes);    }     static int cycleSort(int[] a) {        int writes = 0;         for (int cycleStart = 0; cycleStart < a.length - 1; cycleStart++) {            int val = a[cycleStart];             // count the number of values that are smaller than val            // since cycleStart            int pos = cycleStart;            for (int i = cycleStart + 1; i < a.length; i++)                if (a[i] < val)                    pos++;             // there aren't any            if (pos == cycleStart)                continue;             // skip duplicates            while (val == a[pos])                pos++;             // put val into final position            int tmp = a[pos];            a[pos] = val;            val = tmp;            writes++;             // repeat as long as we can find values to swap            // otherwise start new cycle            while (pos != cycleStart) {                pos = cycleStart;                for (int i = cycleStart + 1; i < a.length; i++)                    if (a[i] < val)                        pos++;                 while (val == a[pos])                    pos++;                 tmp = a[pos];                a[pos] = val;                val = tmp;                writes++;            }        }        return writes;    }}
Output:
[5, 0, 1, 2, 2, 3, 5, 1, 1, 0, 5, 6, 9, 8, 0, 1]
[0, 0, 0, 1, 1, 1, 1, 2, 2, 3, 5, 5, 5, 6, 8, 9]
writes: 14

Kotlin

Translation of the algorithm in the Wikipedia article:

// version 1.1.0 /** Sort an array in place and return the number of writes */fun <T : Comparable<T>> cycleSort(array: Array<T>): Int {    var writes = 0     // Loop through the array to find cycles to rotate.    for (cycleStart in 0 until array.size - 1) {        var item = array[cycleStart]         // Find where to put the item.        var pos = cycleStart        for (i in cycleStart + 1 until array.size) if (array[i] < item) pos++         // If the item is already there, this is not a cycle.        if (pos == cycleStart) continue         // Otherwise, put the item there or right after any duplicates.        while (item == array[pos]) pos++        val temp = array[pos]        array[pos] = item        item = temp        writes++         // Rotate the rest of the cycle.        while (pos != cycleStart) {            // Find where to put the item.            pos = cycleStart            for (i in cycleStart + 1 until array.size) if (array[i] < item) pos++             // Otherwise, put the item there or right after any duplicates.            while (item == array[pos]) pos++            val temp2 = array[pos]            array[pos] = item            item = temp2            writes++        }    }    return writes} fun <T : Comparable<T>> printResults(array: Array<T>) {    println(array.asList())    val writes = cycleSort(array)    println("After sorting with $writes writes:") println(array.asList()) println()} fun main(args: Array<String>) { val array = arrayOf(0, 1, 2, 2, 2, 2, 1, 9, 3, 5, 5, 8, 4, 7, 0, 6) printResults(array) val array2 = arrayOf(5, 0, 1, 2, 2, 3, 5, 1, 1, 0, 5, 6, 9, 8, 0, 1) printResults(array2) val array3 = "the quick brown fox jumps over the lazy dog".split(' ').toTypedArray() printResults(array3) val array4 = "sphinx of black quartz judge my vow".replace(" ", "").toCharArray().distinct().toTypedArray() printResults(array4)} Output: [0, 1, 2, 2, 2, 2, 1, 9, 3, 5, 5, 8, 4, 7, 0, 6] After sorting with 10 writes: [0, 0, 1, 1, 2, 2, 2, 2, 3, 4, 5, 5, 6, 7, 8, 9] [5, 0, 1, 2, 2, 3, 5, 1, 1, 0, 5, 6, 9, 8, 0, 1] After sorting with 14 writes: [0, 0, 0, 1, 1, 1, 1, 2, 2, 3, 5, 5, 5, 6, 8, 9] [the, quick, brown, fox, jumps, over, the, lazy, dog] After sorting with 8 writes: [brown, dog, fox, jumps, lazy, over, quick, the, the] [s, p, h, i, n, x, o, f, b, l, a, c, k, q, u, r, t, z, j, d, g, e, m, y, v, w] After sorting with 26 writes: [a, b, c, d, e, f, g, h, i, j, k, l, m, n, o, p, q, r, s, t, u, v, w, x, y, z]  NetRexx Direct translation of the Wikipedia entry example /* Rexx */options replace format comments java crossref symbols nobinary runSample(arg)return -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~-- Sort an array in place and return the number of writes.method cycleSort(array = Rexx[]) public static writes = 0 -- Loop through the array to find cycles to rotate. loop cycleStart = 0 to array.length - 1 - 1 item = array[cycleStart] -- Find where to put the item. pos = cycleStart loop i = cycleStart + 1 to array.length - 1 if array[i] < item then pos = pos + 1 end i -- If the item is already there, this is not a cycle. if pos == cycleStart then iterate -- Otherwise, put the item there or right after any duplicates. loop while item == array[pos] pos = pos + 1 end swap_tmp = array[pos] array[pos] = item item = swap_tmp writes = writes + 1 -- Rotate the rest of the cycle. loop while pos \= cycleStart -- Find where to put the item. pos = cycleStart loop i = cycleStart + 1 to array.length - 1 if array[i] < item then pos = pos + 1 end i -- Put the item there or right after any duplicates. loop while item == array[pos] pos = pos + 1 end swap_tmp = array[pos] array[pos] = item item = swap_tmp writes = writes + 1 end end cycleStart return writes -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~method runSample(arg) public static samples = ArrayList() samples.add([1, 9, 3, 5, 8, 4, 7, 0, 6, 2]) samples.add([0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]) samples.add(['Greygill Hole', 'Ogof Draenen', 'Ogof Ffynnon Ddu', 'Malham Tarn Pot']) samples.add([-3.14 ,3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9, 3, 2, 3, 8, 4, 6, 2, 6, 4, 3, 3, 8, 3, 2, 7, 9, 5, 0, 2, 8, 8, 4]) samples.add(['George Washington: Virginia', 'John Adams: Massachusetts', 'Thomas Jefferson: Virginia', 'James Madison: Virginia', 'James Monroe: Virginia']) list = Rexx[] loop i_ = 0 to samples.size() - 1 list = Rexx[] samples.get(i_) say 'Input list ' Arrays.asList(list) writes = cycleSort(list) say 'Sorted list' Arrays.asList(list) say 'Total number of writes:' writes say end i_ return  Output: Input list [1, 9, 3, 5, 8, 4, 7, 0, 6, 2] Sorted list [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] Total number of writes: 10 Input list [0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6] Sorted list [0, 0, 1, 1, 2, 2, 2, 2, 3.5, 4, 5, 6, 7, 8, 9] Total number of writes: 10 Input list [Greygill Hole, Ogof Draenen, Ogof Ffynnon Ddu, Malham Tarn Pot] Sorted list [Greygill Hole, Malham Tarn Pot, Ogof Draenen, Ogof Ffynnon Ddu] Total number of writes: 3 Input list [-3.14, 3, 1, 4, 1, 5, 9, 2, 6, 5, 3, 5, 8, 9, 7, 9, 3, 2, 3, 8, 4, 6, 2, 6, 4, 3, 3, 8, 3, 2, 7, 9, 5, 0, 2, 8, 8, 4] Sorted list [-3.14, 0, 1, 1, 2, 2, 2, 2, 2, 3, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 5, 5, 5, 5, 6, 6, 6, 7, 7, 8, 8, 8, 8, 8, 9, 9, 9, 9] Total number of writes: 34 Input list [George Washington: Virginia, John Adams: Massachusetts, Thomas Jefferson: Virginia, James Madison: Virginia, James Monroe: Virginia] Sorted list [George Washington: Virginia, James Madison: Virginia, James Monroe: Virginia, John Adams: Massachusetts, Thomas Jefferson: Virginia] Total number of writes: 4 Objeck Translation of: Java class Test { function : Main(args : String[]) ~ Nil { arr := [5, 0, 1, 2, 2, 3, 5, 1, 1, 0, 5, 6, 9, 8, 0, 1]; arr->ToString()->PrintLine(); writes := CycleSort(arr); "writes: {$writes}"->PrintLine();    arr->ToString()->PrintLine();      }   function : CycleSort(a : Int[]) ~ Int {    writes := 0;     for(cycleStart := 0; cycleStart < a->Size() - 1; cycleStart+=1;) {      val := a[cycleStart];       pos := cycleStart;      for(i := cycleStart + 1; i < a->Size(); i+=1;) {        if(a[i] < val) {          pos++;        };      };       if(pos <> cycleStart) {        while(val = a[pos]) {          pos+=1;        };         tmp := a[pos];        a[pos] := val;        val := tmp;        writes+=1;         while(pos <> cycleStart) {          pos := cycleStart;          for(i := cycleStart + 1; i < a->Size(); i+=1;) {            if(a[i] < val) {              pos+=1;            };          };           while(val = a[pos]) {            pos++;          };           tmp := a[pos];          a[pos] := val;          val := tmp;          writes++;        };      };    };     return writes;  }}
[5,0,1,2,2,3,5,1,1,0,5,6,9,8,0,1]
writes: 14
[0,0,0,1,1,1,1,2,2,3,5,5,5,6,8,9]


ooRexx

/*REXX program demonstrates a cycle sort on a list of numbers*********** 13.06.2014 Walter Pachl* Modified from Rexx Version 2* ooRexx allows to pass a stemmed variable by reference* swapping variables uses a temporary instead of the parse.**********************************************************************/  a.1='George Washington  Virginia'  a.2='John Adams  Massachusetts'  a.3='Thomas Jefferson  Virginia'  a.4='James Madison  Virginia'  a.5='James Monroe  Virginia'  n=5  Call show 'Unsorted list: '  w=sortcycle(a.,n)  Say 'sorted'  Call show 'Sorted list'  Say ' '  Say 'This took' w 'writes.'  Exit sortcycle: Procedure  Use Arg a.,n  writes=0  Do c=1 For n    x=a.c    p=c    x=a.c    Do j=c+1 To n      If a.j<x Then        p=p+1      End    If p==c Then      Iterate    Do While x==a.p      p=p+1      End    t=x    x=a.p    a.p=t    writes=writes+1    Do While p\==c      p=c      Do k=c+1 To n        If a.k<x Then          p=p+1        End      Do While x==a.p        p=p+1        End      t=x      x=a.p      a.p=t      writes=writes+1      End    End  Return writes show:  Parse Arg hdr  Say ' '  Say hdr  Do i=1 To n    Say format(i,2) a.i    End  Return
Output:
Unsorted list:
1 George Washington  Virginia
3 Thomas Jefferson  Virginia
5 James Monroe  Virginia
sorted

Sorted list
1 George Washington  Virginia
3 James Monroe  Virginia
5 Thomas Jefferson  Virginia

This took 4 writes.

Perl

This is based on the Wikipedia pseudocode.

use strict;use warnings; sub cycleSort(@) {	my ($array) = @_; my$writes = 0; 	my @alreadysorted; 	# For each index except the last:	for my $start ( 0 ..$#$array - 1 ) { next if$alreadysorted[$start]; my$item = $array->[$start];		# If there are N items less than $item, then we # must move$item N items rightward.		my $pos =$start + grep $array->[$_] lt $item,$start + 1 .. $#$array;		# If the item is where it should be, continue.		next if $pos ==$start;		# If $item is one of several repetitions, move it to the right # of the last repeat. ++$pos while $item eq$array->[ $pos ]; # Store$item at $pos, where it belongs, and fetch the # value that had been at$pos, and put it in $item. ($array->[ $pos ],$item) = ($item,$array->[ $pos ]); ++$writes; 		# Whatever $item is now, it certainly doesn't belong at$pos;		do {			# Find the correct $pos,$pos = $start + grep$array->[$_] lt$item, $start+1 ..$#$array; ++$pos while $item eq$array->[ $pos ]; # Swap the value there with$item,			($array->[$pos ] , $item ) = ($item, $array->[$pos ]);			# And mark $pos as having the correct value in it..$alreadysorted[ $pos ] = 1; ++$writes;			# The loop ends after we have just written an item to $start } while$pos != $start; }$writes;} use List::Util 'shuffle';my @test = shuffle( ('a'..'z') x 2 );print "Before sorting: @test\n";print "There were ", cycleSort( \@test ), " writes\n";print "After  sorting: @test\n";
Output:
Before sorting: a t d b f g y l t p w c r r x i y j k i z q e v a f o q j u x k m h s u v z g m b o l e n h p n c s w d
There were 50 writes
After  sorting: a a b b c c d d e e f f g g h h i i j j k k l l m m n n o o p p q q r r s s t t u u v v w w x x y y z z

Perl 6

sub cycle_sort ( @nums ) {    my $writes = 0; # Loop through the array to find cycles to rotate. for @nums.kv ->$cycle_start, $item is copy { # Find where to put the item. my$pos = $cycle_start + @nums[$cycle_start ^.. * ].grep: * < $item; # If the item is already there, this is not a cycle. next if$pos == $cycle_start; # Otherwise, put the item there or right after any duplicates.$pos++ while $item == @nums[$pos];        ( @nums[$pos],$item ) .= reverse;        $writes++; # Rotate the rest of the cycle. while$pos != $cycle_start { # Find where to put the item.$pos = $cycle_start + @nums[$cycle_start ^.. * ].grep: * < $item; # Put the item there or right after any duplicates.$pos++ while $item == @nums[$pos];            ( @nums[$pos],$item ) .= reverse;            $writes++; } } return$writes;} my @a = <0 1 2 2 2 2 1 9 3.5 5 8 4 7 0 6>; say @a;say 'writes ', cycle_sort(@a);say @a;
Output:
0 1 2 2 2 2 1 9 3.5 5 8 4 7 0 6
writes 10
0 0 1 1 2 2 2 2 3.5 4 5 6 7 8 9


Python

The Wikipedia algorithm pseudocode is very nearly Python. The main changes needed were to change the name array to vector to stop it obscuring a built-in name, and iterating over an enumerated collection rather than using explicit indices.

def cycleSort(vector):    "Sort a vector in place and return the number of writes."    writes = 0     # Loop through the vector to find cycles to rotate.    for cycleStart, item in enumerate(vector):         # Find where to put the item.        pos = cycleStart        for item2 in vector[cycleStart + 1:]:            if item2 < item:                pos += 1         # If the item is already there, this is not a cycle.        if pos == cycleStart:            continue         # Otherwise, put the item there or right after any duplicates.        while item == vector[pos]:            pos += 1        vector[pos], item = item, vector[pos]        writes += 1         # Rotate the rest of the cycle.        while pos != cycleStart:             # Find where to put the item.            pos = cycleStart            for item2 in vector[cycleStart + 1:]:                if item2 < item:                    pos += 1             # Put the item there or right after any duplicates.            while item == vector[pos]:                pos += 1            vector[pos], item = item, vector[pos]            writes += 1     return writes  if __name__ == '__main__':    x = [0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]    xcopy = x[::]    writes = cycleSort(xcopy)    if xcopy != sorted(x):        print('Wrong order!')    else:        print('%r\nIs correctly sorted using cycleSort to'              '\n%r\nUsing %i writes.' % (x, xcopy, writes))
Output:
[0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]
Is correctly sorted using cycleSort to
[0, 0, 1, 1, 2, 2, 2, 2, 3.5, 4, 5, 6, 7, 8, 9]
Using 10 writes.

Racket

#lang racket/base(require racket/match) ;; Sort an array in place and return the number of writes.(define (cycle-sort! v < =?)  (define v-len (vector-length v))  (for/sum ; Loop through the array to find cycles to rotate.    ((cycle-start (in-range 0 (sub1 v-len))))    (define item (vector-ref v cycle-start))    (define (find-insertion-point) ; Find where to put the item.          (+ cycle-start         (for/sum            ((i (in-range (add1 cycle-start) v-len))            #:when (< (vector-ref v i) item)) 1)))    ;; Put the item there or right after any duplicates    (define (insert-after-duplicates pos)      (match (vector-ref v pos)        [(== item =?) (insert-after-duplicates (add1 pos))]        [tmp (vector-set! v pos item) ; / swap             (set! item tmp)          ; \ [this is my only write point]             pos]))     (define i-p (find-insertion-point))    (if (= i-p cycle-start)        0 ; If the item is already there, this is not a cycle.        (let loop ; Rotate the rest of the cycle.                  ((e-p (insert-after-duplicates i-p))           (W 1 #| we've already written once |#))          (if (= e-p cycle-start)              W              (loop (insert-after-duplicates (find-insertion-point))                    (add1 W))))))) ; we've written again! (module+ main  ;; This will be random with duplicates  (define A (list->vector (build-list 30 (λ (i) (random 20)))))  A  (cycle-sort! A < =)  A  (define B #(1 1 1 1 1 1))  B  (cycle-sort! B < =))
Output:
'#(7 17 5 16 14 9 18 10 1 4 10 1 9 3 3 0 1 18 16 12 9 14 14 12 19 2 12 15 16 8)
28
'#(0 1 1 1 2 3 3 4 5 7 8 9 9 9 10 10 12 12 12 14 14 14 15 16 16 16 17 18 18 19)
'#(1 1 1 1 1 1)
0

REXX

 This example is incorrect. Please fix the code and remove this message.Details: The program yields syntax errors. The program uses non-ANSI form for assignment (addition). The program uses a non-ANSI format of comments.

version 1

/* REXX **************************************************************** 12.06.2014 Walter Pachl translated from Wikipedia's code* 20.06.2014 WP corrected (courtesy Alan Sampson)**********************************************************************/list='1 9 3 5 8 4 7 0 6 2'n=words(list)Do i=0 To n-1  array.i=word(list,i+1)  EndSay listwrites=cyclesort()Say 'writes='writesol=''Do i=0 To n-1  ol=ol array.i  EndSay strip(ol)Exit cycleSort: procedure expose array. n  writes = 0  -- Loop through the array to find cycles to rotate.  do cycleStart=0 to n-2    item = array.cycleStart     -- Find where to put the item.    pos = cycleStart    Do i=cycleStart+1 to n-1      if array.i < item Then        pos += 1      End     -- If the item is already there, this is not a cycle.    if pos == cycleStart Then      Iterate     -- Otherwise, put the item there or right after any duplicates.    Do while item == array.pos      pos += 1      End    Parse Value array.pos item With item array.pos    writes += 1     -- Rotate the rest of the cycle.    Do while pos <> cycleStart       -- Find where to put the item.      pos = cycleStart      Do i=cycleStart + 1 to n-1        if array.i < item Then          pos += 1        End       -- Put the item there or right after any duplicates.      Do while item == array.pos        pos += 1        End      Parse Value array.pos item With item array.pos      writes += 1      End    End  return writes
Output:
1 9 3 5 8 4 7 0 6 2
writes=10
0 1 2 3 4 5 6 7 8 9

version 2

This REXX version demonstrates the use of negative numbers and non-integer values in the list.

As a default, the program uses (for the input list) some digits of pi, which for practical purposes, appear random.

/*REXX program demonstrates a  cycle sort  on a  list of items.                         */parse arg z                                      /* [↓] not specified?  Use "pi" digits.*/if z='' then z=-3.14 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4 6 2 6 4 3 3 8 3 2 7 9 5 0 2 8 8 4say 'unsorted list: '  z                         /*show the original unsorted numbers.  */w=sortCycle(z)                                   /*W:  the number of writes done in sort*/say 'and took'  w  "writes."                     /*show number of writes done in sort.  */exit                                             /*stick a fork in it,  we're all done. *//*──────────────────────────────────────────────────────────────────────────────────────*/sortCycle: procedure expose @.;  parse arg y;          #=words(y);   writes=0        do i=1  for #; @.i=word(y,i); end  /*i*/ /*put each of the items ───► @.  array.*/                                                 /* [↓]  find a  "cycle"  to rotate.    */  do c=1  for #;    x=@.c;         p=c           /*X  is the  item  being sorted.       */        do j=c+1  to #; if @.j<x  then p=p+1; end        /*determine where to put  X.   */  if p==c then  iterate                          /*Is it there?  No, this ain't a cycle.*/        do  while x==@.p;  p=p+1;  end           /*put  X  right after any duplicate.   */  parse value  @.p  x    with  x  @.p            /*swap the two values:   @.p   and   X.*/  writes=writes+1                                /*bump counter for the number of writes*/      do while p\==c;     p=c                    /*rotate the rest of the "cycle".      */        do k=c+1  to #;   if @.k<x  then p=p+1;  end  /*k*/        do while x==@.p;  p=p+1;  end            /*put  X  here  or  right after dups.  */      parse value  @.p  x    with    x  @.p      /*swap the two values:   @.p   and   X.*/      writes=writes+1                            /*bump the counter for number of writes*/      end   /*while p\==c*/  end       /*c*/                                                 /* [↓]  display the sorted list.       */_=@.1;  do j=2  to #; _=_ @.j; end;       say '  sorted list: '  _return writes

output   when using the default input:

unsorted list:  -3.14 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4 6 2 6 4 3 3 8 3 2 7 9 5 0 2 8 8 4
sorted list:  -3.14 0 1 1 2 2 2 2 2 3 3 3 3 3 3 3 4 4 4 4 5 5 5 5 6 6 6 7 7 8 8 8 8 8 9 9 9 9
and took 34 writes.


output   when using the input of:   FM Stereo has been around since 1961.

unsorted list:  FM Stereo has been around since 1961.
sorted list:  1961. FM Stereo around been has since
and took 7 writes.


Note (for the above output).   This REXX program was executed on an ASCII machine.
On an   ASCII   machine, the order of sorting is numbers, uppercase letters, lowercase letters.
On an EBCDIC machine, the order of sorting is lowercase letters, uppercase letters, numbers.
Other (special) characters may also be in a different order.

version 3

This version uses a faster (but a more cryptic) version of incrementing   1   (one) to   P   within two do loops.

/*REXX program demonstrates a  cycle sort  on a  list of items.                         */parse arg z                                      /* [↓] not specified?  Use "pi" digits.*/if z='' then z=-3.14 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4 6 2 6 4 3 3 8 3 2 7 9 5 0 2 8 8 4say 'unsorted list: '  z                         /*show the original unsorted numbers.  */w=sortCycle(z)                                   /*W:  the number of writes done in sort*/say 'and took'  w  "writes."                     /*show number of writes done in sort.  */exit                                             /*stick a fork in it,  we're all done. *//*──────────────────────────────────────────────────────────────────────────────────────*/sortCycle: procedure expose @.;  parse arg y;          #=words(y);   writes=0        do i=1  for #; @.i=word(y,i); end  /*i*/ /*put each of the items ───► @.  array.*/                                                 /* [↓]  find a  "cycle"  to rotate.    */  do c=1  for #;    x=@.c;         p=c           /*X  is the  item  being sorted.       */        do j=c+1  to #; if @.j<x  then p=p+1; end        /*determine where to put  X.   */  if p==c then  iterate                          /*Is it there?  No, this ain't a cycle.*/        do  while x==@.p;  p=p+1;  end           /*put  X  right after any duplicate.   */  parse value  @.p  x    with  x  @.p            /*swap the two values:   @.p   and   X.*/  writes=writes+1                                /*bump counter for the number of writes*/      do while p\==c;     p=c                    /*rotate the rest of the "cycle".      */        do k=c+1  to #;   if @.k<x  then p=p+1;  end  /*k*/        do p=p  while x==@.p;  end               /*put   X   here  or  right after dups.*/      parse  value  @.p  x   with   x  @.p       /*swap the two values:   @.p   and   X.*/      writes=writes+1                            /*bump the counter for number of writes*/      end   /*while p\==c*/  end       /*c*/                                                 /* [↓]  display the sorted list.       */_=@.1;  do j=2  to #; _=_ @.j; end;           say '  sorted list: '  _return writes

output is identical to the 2nd version.

version 4

This version uses a subroutine to perform the task of handling an (sorted) item placement (possibly after duplicates).

/*REXX program demonstrates a  cycle sort  on a  list of items.                         */parse arg z                                      /* [↓] not specified?  Use "pi" digits.*/if z='' then z=-3.14 3 1 4 1 5 9 2 6 5 3 5 8 9 7 9 3 2 3 8 4 6 2 6 4 3 3 8 3 2 7 9 5 0 2 8 8 4say 'unsorted list: '  z                         /*show the original unsorted numbers.  */w=sortCycle(z)                                   /*W:  the number of writes done in sort*/say 'and took'  w  "writes."                     /*show number of writes done in sort.  */exit                                             /*stick a fork in it,  we're all done. *//*──────────────────────────────────────────────────────────────────────────────────────*/sortCycle: procedure expose @.;    parse arg y;   #=words(y);      w=0        do i=1  for #; @.i=word(y,i); end  /*i*/ /*put each of the items ───► @.  array.*/   do c=1  for #;     x=@.c;      p=c             /*X  is the  item  being sorted.       */      do j=c+1  to #; if @.j<x  then p=p+1; end  /*j*/                /*where to put  X.*/  if p==c  then  iterate                         /*Is it there?  Then this ain't a cycle*/  call .swap                                     /*put   X   here  or  right after dups.*/      do while p\==c;     p=c                    /*rotate the rest of the  "cycle".     */        do k=c+1  to #;   if @.k<x  then p=p+1;  end  /*k*/      call .swap                                 /*put   X   here  or  right after dups.*/      end   /*while p\==c*/  end       /*c*/                                                 /* [↓]  display the sorted list to term*/_=@.1;  do j=2  to #; _=_ @.j; end;       say '  sorted list: '  _return w                                         /* [↓] find where to put   X   into  @ */.swap:  do p=p  while x==@.p;  end;       parse value  @.p x  with  x @.p;  w=w+1;  return

output   is identical to the 2nd version.

Ruby

Direct translation of the pseudocode on the Wikipedia.

def cycleSort!(array)  writes = 0   # Loop through the array to find cycles to rotate.  for cycleStart in 0 .. array.size-2    item = array[cycleStart]     # Find where to put the item.    pos = cycleStart    for i in cycleStart+1 ... array.size      pos += 1  if array[i] < item    end     # If the item is already there, this is not a cycle.    next  if pos == cycleStart     # Otherwise, put the item there or right after any duplicates.    pos += 1  while item == array[pos]    array[pos], item = item, array[pos]    writes += 1     # Rotate the rest of the cycle.    while pos != cycleStart       # Find where to put the item.      pos = cycleStart      for i in cycleStart+1 ... array.size        pos += 1  if array[i] < item      end       # Put the item there or right after any duplicates.      pos += 1  while item == array[pos]      array[pos], item = item, array[pos]      writes += 1    end  end  writesend  p a = [0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]puts "writes : #{cycleSort!(a)}"p a
Output:
[0, 1, 2, 2, 2, 2, 1, 9, 3.5, 5, 8, 4, 7, 0, 6]
writes : 10
[0, 0, 1, 1, 2, 2, 2, 2, 3.5, 4, 5, 6, 7, 8, 9]


Scala

Translation of Java version

   def cycleSort(a: Array[Int]): (Array[Int], Int) = {    var writes = 0     for (cycleStart <- 0 until a.length - 1) {      var value = a(cycleStart)       // count the number of values that are smaller than value since cycleStart      var pos = cycleStart       for (i <- cycleStart + 1 until a.length)        if (a(i) < value) pos += 1       // skip if there aren't any      if (pos != cycleStart) {         // skip duplicates        while (a(pos) == value) pos += 1         // put val into final position        val tmp = a(pos)        a(pos) = value        value = tmp        writes += 1         // repeat as long as we can find values to swap        // otherwise start new cycle        while (pos != cycleStart) {          pos = cycleStart          for (i <- cycleStart + 1 until a.length)            if (a(i) < value) pos += 1           while (a(pos) == value) pos += 1           val tmp = a(pos)          a(pos) = value          value = tmp          writes += 1        }      }    }    (a, writes)  }

Sidef

func cycle_sort (array) {    var (writes=0, pos=0)     func f(i, Ref item, bool=false) {        pos = (i + array.ft(i+1).count{ _ < *item })        return(false) if (bool && pos==i)        while (*item == array[pos]) { ++pos }        (array[pos], *item) = (*item, array[pos])        ++writes        return true    }     array.each_kv { |i, item|        f(i, \item, true) || next        while (pos != i) {            f(i, \item)        }    }     return writes} var a = %n(0 1 2 2 2 2 1 9 3.5 5 8 4 7 0 6) say a.join(' ')say ('writes ', cycle_sort(a))say a.join(' ')
Output:
0 1 2 2 2 2 1 9 3.5 5 8 4 7 0 6
writes 10
0 0 1 1 2 2 2 2 3.5 4 5 6 7 8 9


Tcl

proc cycleSort {listVar} {    upvar 1 $listVar array set writes 0 # Loop through the array to find cycles to rotate. for {set cycleStart 0} {$cycleStart < [llength $array]} {incr cycleStart} { set item [lindex$array $cycleStart] # Find where to put the item. set pos$cycleStart	for {set i [expr {$pos + 1}]} {$i < [llength $array]} {incr i} { incr pos [expr {[lindex$array $i] <$item}]	} 	# If the item is already there, this is not a cycle.	if {$pos ==$cycleStart} continue 	# Otherwise, put the item there or right after any duplicates.	while {$item == [lindex$array $pos]} { incr pos } set tmp [lindex$array $pos] lset array$pos $item set item$tmp	incr writes 	# Rotate the rest of the cycle.	while {$pos !=$cycleStart} {	    # Find where to put the item.	    set pos $cycleStart for {set i [expr {$cycleStart + 1}]} {$i < [llength$array]} {incr i} {		incr pos [expr {[lindex $array$i] < $item}] } # Put the item there or right after any duplicates. while {$item == [lindex $array$pos]} {		incr pos	    }	    set tmp [lindex $array$pos]	    lset array $pos$item	    set item $tmp incr writes } } return$writes}
set example {0 1 2 2 2 2 1 9 3.5 5 8 4 7 0 6}puts "Data was: $example"set writes [cycleSort example]puts "Data is now:$example"if {$example eq [lsort -real$example]} {    puts "\twhich is correctly sorted"} else {    puts "\twhich is the wrong order!"}puts "Writes required: \$writes"
Data was: 0 1 2 2 2 2 1 9 3.5 5 8 4 7 0 6