Sorting algorithms/Bogosort: Difference between revisions
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std::random_shuffle(begin, end);
}</lang>
Using the is_sorted function, part of the SGI STL implementation and C++11:
{{works with|GCC}}
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Revision as of 06:57, 28 September 2011
You are encouraged to solve this task according to the task description, using any language you may know.
Sorting Algorithm
This is a sorting algorithm. It may be applied to a set of data in order to sort it.
For comparing various sorts, see compare sorts.
For other sorting algorithms, see sorting algorithms, or:
Heap sort | Merge sort | Patience sort | Quick sort
O(n log2n) sorts
Shell Sort
O(n2) sorts
Bubble sort |
Cocktail sort |
Cocktail sort with shifting bounds |
Comb sort |
Cycle sort |
Gnome sort |
Insertion sort |
Selection sort |
Strand sort
other sorts
Bead sort |
Bogo sort |
Common sorted list |
Composite structures sort |
Custom comparator sort |
Counting sort |
Disjoint sublist sort |
External sort |
Jort sort |
Lexicographical sort |
Natural sorting |
Order by pair comparisons |
Order disjoint list items |
Order two numerical lists |
Object identifier (OID) sort |
Pancake sort |
Quickselect |
Permutation sort |
Radix sort |
Ranking methods |
Remove duplicate elements |
Sleep sort |
Stooge sort |
[Sort letters of a string] |
Three variable sort |
Topological sort |
Tree sort
Bogosort a list of numbers. Bogosort simply shuffles a collection randomly until it is sorted.
It is worth noting that "Bogosort" is a perversely inefficient algorithm and only used as an "in joke". Its expected run-time efficiency would be O(n!) because the chance that any given shuffle of a set will end up in sorted order is about one in n factorial, and the worst case is infinite since there's no guarantee that a random shuffling will ever produce a sorted sequence.
Pseudocode:
while not InOrder(list) do Shuffle(list) done
See also
- Knuth shuffle (which may be used to implement the shuffle part of this algorithm)
ActionScript
<lang actionscript>public function bogoSort(arr:Array):Array {
while (!sorted(arr)) { shuffle(arr); }
return arr;
}
public function shuffle(arr:Array):void {
for (var i:int = 0; i < arr.length; i++) { var rand:int = Math.floor(Math.random() * arr.length); var tmp:* = arr[i]; arr[i] = arr[rand]; arr[rand] = tmp; }
}
public function sorted(arr:Array):Boolean {
var last:int = arr[0];
for (var i:int = 1; i < arr.length; i++) { if (arr[i] < last) { return false; }
last = arr[i]; }
return true;
}</lang>
Ada
<lang ada>with Ada.Text_IO; use Ada.Text_IO; with Ada.Numerics.Discrete_Random;
procedure Test_Bogosort is
generic type Ordered is private; type List is array (Positive range <>) of Ordered; with function "<" (L, R : Ordered) return Boolean is <>; procedure Bogosort (Data : in out List);
procedure Bogosort (Data : in out List) is function Sorted return Boolean is begin for I in Data'First..Data'Last - 1 loop if not (Data (I) < Data (I + 1)) then return False; end if; end loop; return True; end Sorted; subtype Index is Integer range Data'Range; package Dices is new Ada.Numerics.Discrete_Random (Index); use Dices; Dice : Generator; procedure Shuffle is J : Index; Temp : Ordered; begin for I in Data'Range loop J := Random (Dice); Temp := Data (I); Data (I) := Data (J); Data (J) := Temp; end loop; end Shuffle; begin while not Sorted loop Shuffle; end loop; end Bogosort;
type List is array (Positive range <>) of Integer; procedure Integer_Bogosort is new Bogosort (Integer, List); Sequence : List := (7,6,3,9);
begin
Integer_Bogosort (Sequence); for I in Sequence'Range loop Put (Integer'Image (Sequence (I))); end loop;
end Test_Bogosort;</lang> The solution is generic. The procedure Bogosort can be instantiated with any copyable comparable type. In the example given it is the standard Integer type. Sample output:
3 6 7 9
ALGOL 68
<lang algol68>MODE TYPE = INT;
PROC random shuffle = (REF[]TYPE l)VOID: (
INT range = UPB l - LWB l + 1; FOR index FROM LWB l TO UPB l DO TYPE tmp := l[index]; INT other := ENTIER (LWB l + random * range); l[index] := l[other]; l[other] := tmp OD
);
PROC in order = (REF[]TYPE l)BOOL: (
IF LWB l >= UPB l THEN TRUE ELSE TYPE last := l[LWB l]; FOR index FROM LWB l + 1 TO UPB l DO IF l[index] < last THEN GO TO return false FI; last := l[index] OD; TRUE EXIT return false: FALSE FI
);
PROC bogo sort = (REF[]TYPE l)REF[]TYPE: (
WHILE NOT in order(l) DO random shuffle(l) OD; l
);
[6]TYPE sample := (61, 52, 63, 94, 46, 18); print((bogo sort(sample), new line))</lang> Output:
+18 +46 +52 +61 +63 +94
AutoHotkey
<lang AutoHotkey>MsgBox % Bogosort("987654") MsgBox % Bogosort("319208") MsgBox % Bogosort("fedcba") MsgBox % Bogosort("gikhjl")
Bogosort(sequence) {
While !Sorted(sequence) sequence := Shuffle(sequence) Return sequence
}
Sorted(sequence) {
Loop, Parse, sequence { current := A_LoopField rest := SubStr(sequence, A_Index) Loop, Parse, rest { If (current > A_LoopField) Return false } } Return true
}
Shuffle(sequence) {
Max := StrLen(sequence) + 1 Loop % StrLen(sequence) { Random, Num, 1, % Max - A_Index Found .= SubStr(sequence, Num, 1) sequence := SubStr(sequence, 1, Num-1) . SubStr(sequence, Num+1) } Return Found
}</lang>
AWK
Sort standard input and output to the standard output <lang awk>function randint(n) {
return int(n * rand())
}
function sorted(sa, sn) {
for(si=1; si < sn; si++) { if ( sa[si] > sa[si+1] ) return 0; } return 1
}
{
line[NR] = $0
} END { # sort it with bogo sort
while ( sorted(line, NR) == 0 ) { for(i=1; i <= NR; i++) { r = randint(NR) + 1 t = line[i] line[i] = line[r] line[r] = t } } #print it for(i=1; i <= NR; i++) { print line[i] }
}</lang>
Brat
<lang brat>bogosort = { list | sorted = list.sort #Kinda cheating here while { list != sorted } { list.shuffle! } list }
p bogosort [15 6 2 9 1 3 41 19]</lang>
C
<lang c>#include <stdio.h>
- include <stdlib.h>
- include <stdbool.h>
bool is_sorted(int *a, int n) {
while ( --n >= 1 ) { if ( a[n] < a[n-1] ) return false; } return true;
}
void shuffle(int *a, int n) {
int i, t, r; for(i=0; i < n; i++) { t = a[i]; r = rand() % n; a[i] = a[r]; a[r] = t; }
}
void bogosort(int *a, int n) {
while ( !is_sorted(a, n) ) shuffle(a, n);
}
int main() {
int numbers[] = { 1, 10, 9, 7, 3, 0 }; int i;
bogosort(numbers, 6); for (i=0; i < 6; i++) printf("%d ", numbers[i]); printf("\n");
}</lang>
C++
The following algorithm actually works for all sequences of comparable types; restricting to lists of integers would not make the code simpler. <lang cpp>#include <iterator>
- include <algorithm>
template<typename ForwardIterator>
void bogosort(ForwardIterator begin, ForwardIterator end)
{
typedef std::iterator_traits<ForwardIterator>::value_type value_type;
// if we find two adjacent values where the first is greater than the second, the sequence isn't sorted. while (std::adjacent_find(begin, end, std::greater<value_type>()) != end) std::random_shuffle(begin, end);
}</lang> Using the is_sorted function, part of the SGI STL implementation and C++11:
<lang cpp>#include <algorithm>
- include <ext/algorithm>
template<typename ForwardIterator>
void bogosort(ForwardIterator begin, ForwardIterator end)
{
while (!__gnu_cxx::is_sorted(begin, end)) std::random_shuffle(begin, end);
}</lang>
C#
<lang csharp>using System; using System.Collections.Generic;
namespace RosettaCode.BogoSort {
public static class BogoSorter { public static void Sort<T>(List<T> list) where T:IComparable { while (!list.isSorted()) { list.Shuffle(); } }
private static bool isSorted<T>(this IList<T> list) where T:IComparable { if(list.Count<=1) return true; for (int i = 1 ; i < list.Count; i++) if(list[i].CompareTo(list[i-1])<0) return false; return true; }
private static void Shuffle<T>(this IList<T> list) { Random rand = new Random(); for (int i = 0; i < list.Count; i++) { int swapIndex = rand.Next(list.Count); T temp = list[swapIndex]; list[swapIndex] = list[i]; list[i] = temp; } } }
class TestProgram { static void Main() { List<int> testList = new List<int> { 3, 4, 1, 8, 7, 4, -2 }; BogoSorter.Sort(testList); foreach (int i in testList) Console.Write(i + " "); }
}
}</lang>
Clojure
We use seq-utils' shuffle, which initializes a Java ArrayList with the input sequence, shuffle it, and then return a sequence of the result.
<lang clojure>(ns bogosort
(:use [clojure.contrib.seq-utils :only (shuffle)]))
(defn in-order? [less xs]
(or (empty? xs) (empty? (next xs)) (and (less (first xs) (second xs)) (recur less (next xs)))))
(defn bogosort
([xs] (bogosort < xs)) ([less xs] (if (in-order? less xs) xs
(recur less (shuffle xs)))))
(println (bogosort [7,5,12,1,4,2,23,18]))</lang>
Common Lisp
Sortedp checks that each element of a list is related by predicate to the next element of the list. I.e., (sortedp (x1 x2 … xn) pred)
is true when each of (pred x1 x2)
, …, (pred xn-1 xn)
is true.
nshuffle
is the same code as in Knuth shuffle.
<lang lisp>(defun nshuffle (sequence)
(loop for i from (length sequence) downto 2 do (rotatef (elt sequence (random i)) (elt sequence (1- i )))) sequence)
(defun sortedp (list predicate)
(every predicate list (rest list)))
(defun bogosort (list predicate)
(do ((list list (nshuffle list))) ((sortedp list predicate) list)))</lang>
D
<lang d>import std.stdio, std.algorithm, std.random;
void bogoSort(T)(T[] data) {
while (!isSorted(data)) randomShuffle(data);
}
void main() {
auto array = [2, 7, 41, 11, 3, 1, 6, 5, 8]; bogoSort(array); writeln(array);
}</lang> Output:
[1, 2, 3, 5, 6, 7, 8, 11, 41]
E
Using the shuffle from Knuth shuffle#E.
<lang e>def isSorted(list) {
if (list.size() == 0) { return true } var a := list[0] for i in 1..!(list.size()) { var b := list[i] if (a > b) { return false } a := b } return true
}
def bogosort(list, random) {
while (!isSorted(list)) { shuffle(list, random) }
}</lang>
Euphoria
<lang euphoria>function shuffle(sequence s)
object temp integer j for i = length(s) to 1 by -1 do j = rand(i) if i != j then temp = s[i] s[i] = s[j] s[j] = temp end if end for return s
end function
function inOrder(sequence s)
for i = 1 to length(s)-1 do if compare(s[i],s[i+1]) > 0 then return 0 end if end for return 1
end function
function bogosort(sequence s)
while not inOrder(s) do ? s s = shuffle(s) end while return s
end function
? bogosort(shuffle({1,2,3,4,5,6}))</lang>
Output:
{1,2,5,4,6,3} {5,1,3,6,2,4} {4,6,1,2,5,3} ............. {1,2,6,5,4,3} {5,3,1,2,6,4} {1,2,3,4,5,6}
Factor
<lang factor>USING: grouping kernel math random sequences ;
- sorted? ( seq -- ? ) 2 <clumps> [ first2 <= ] all? ;
- bogosort ( seq -- newseq ) [ dup sorted? ] [ randomize ] until ;</lang>
Fortran
<lang fortran>MODULE BOGO IMPLICIT NONE CONTAINS
FUNCTION Sorted(a) LOGICAL :: Sorted INTEGER, INTENT(IN) :: a(:) INTEGER :: i
Sorted = .TRUE. DO i = 1, SIZE(a)-1 IF(a(i) > a(i+1)) THEN Sorted = .FALSE. EXIT END IF END DO END FUNCTION Sorted
SUBROUTINE SHUFFLE(a) INTEGER, INTENT(IN OUT) :: a(:) INTEGER :: i, rand, temp REAL :: x
DO i = SIZE(a), 1, -1 CALL RANDOM_NUMBER(x) rand = INT(x * i) + 1 temp = a(rand) a(rand) = a(i) a(i) = temp END DO END SUBROUTINE
END MODULE
PROGRAM BOGOSORT
USE BOGO IMPLICIT NONE INTEGER :: iter = 0 INTEGER :: array(8) = (/2, 7, 5, 3, 4, 8, 6, 1/) LOGICAL :: s DO s = Sorted(array) IF (s) EXIT CALL SHUFFLE(array) iter = iter + 1 END DO WRITE (*,*) "Array required", iter, " shuffles to sort"
END PROGRAM BOGOSORT</lang>
Go
<lang go>package main
import (
"fmt" "rand" "time" "sort"
)
func main() {
list := []int{31, 41, 59, 26, 53, 58, 97, 93, 23, 84} fmt.Println("unsorted:", list) temp := make([]int, len(list)) rand.Seed(time.Nanoseconds()) for !sort.IntsAreSorted(list) { for i, v := range rand.Perm(len(list)) { temp[i] = list[v] } copy(list, temp) } fmt.Println("sorted! ", list)
}</lang> Output: (sometimes takes a few seconds)
unsorted: [31 41 59 26 53 58 97 93 23 84] sorted! [23 26 31 41 53 58 59 84 93 97]
Groovy
Solution (also implicitly tracks the number of shuffles required): <lang groovy>def bogosort = { list ->
def n = list.size() while (n > 1 && (1..<n).any{ list[it-1] > list[it] }) { print '.'*n Collections.shuffle(list) } list
}</lang>
Test Program: <lang groovy>println (bogosort([3,1,2]))</lang>
Output, trial 1:
..............................[1, 2, 3]
Output, trial 2:
...................................................[1, 2, 3]
Haskell
<lang haskell>import System.Random import Data.Array.IO import Control.Monad
isSorted :: (Ord a) => [a] -> Bool isSorted (e1:e2:r) = e1 <= e2 && isSorted (e2:r) isSorted _ = True
-- from http://www.haskell.org/haskellwiki/Random_shuffle shuffle :: [a] -> IO [a] shuffle xs = do
ar <- newArray n xs forM [1..n] $ \i -> do j <- randomRIO (i,n) vi <- readArray ar i vj <- readArray ar j writeArray ar j vi return vj where n = length xs newArray :: Int -> [a] -> IO (IOArray Int a) newArray n xs = newListArray (1,n) xs
bogosort :: (Ord a) => [a] -> IO [a] bogosort li | isSorted li = return li
| otherwise = shuffle li >>= bogosort</lang>
Example:
*Main> bogosort [7,5,12,1,4,2,23,18] [1,2,4,5,7,12,18,23]
Icon and Unicon
<lang icon>procedure shuffle(l)
repeat { !l :=: ?l suspend l }
end
procedure sorted(l)
local i if (i := 2 to *l & l[i] >= l[i-1]) then return &fail else return 1
end
procedure main()
local l l := [6,3,4,5,1] |( shuffle(l) & sorted(l)) \1 & every writes(" ",!l)
end</lang>
Io
<lang io>List do(
isSorted := method( slice(1) foreach(i, x, if (x < at(i), return false) ) return true; )
bogoSortInPlace := method( while(isSorted not, shuffleInPlace() ) )
)
lst := list(2, 1, 4, 3) lst bogoSortInPlace println # ==> list(1, 2, 3, 4), hopefully :)</lang>
J
<lang j>bogo=: monad define
whilst. +./ 2 >/\ Ry do. Ry=. (A.~ ?@!@#) y end. Ry
)</lang>
Java
This implementation works for all comparable types (types with compareTo defined). <lang java5>import java.util.Collections; import java.util.List; import java.util.Iterator;
public class Bogosort {
private static <T extends Comparable<? super T>> boolean isSorted(List<T> list) { if (list.isEmpty()) return true; Iterator<T> it = list.iterator(); T last = it.next(); while (it.hasNext()) { T current = it.next(); if (last.compareTo(current) > 0) return false; last = current; } return true; }
public static <T extends Comparable<? super T>> void bogoSort(List<T> list) { while (!isSorted(list)) Collections.shuffle(list); }
}</lang>
JavaScript
<lang javascript>shuffle = function(v) {
for(var j, x, i = v.length; i; j = Math.floor(Math.random() * i), x = v[--i], v[i] = v[j], v[j] = x); return v;
};
isSorted = function(v){
for(var i=1; i<v.length; i++) { if (v[i-1] > v[i]) { return false; } } return true;
}
bogosort = function(v){
var sorted = false; while(sorted == false){ v = shuffle(v); sorted = isSorted(v); } return v;
}</lang>
Lua
<lang lua>function bogosort (list)
if type (list) ~= 'table' then return list end
-- Fisher-Yates Knuth shuffle local function shuffle () local rand = math.random(1,#list) for i=1,#list do list[i],list[rand] = list[rand],list[i] rand = math.random(1,#list) end end
-- Returns true only if list is now sorted local function in_order () local last = list[1] for i,v in next,list do if v < last then return false end last = v end return true end
while not in_order() do shuffle() end
return list
end</lang>
M4
<lang M4>divert(-1) define(`randSeed',141592653) define(`setRand',
`define(`randSeed',ifelse(eval($1<10000),1,`eval(20000-$1)',`$1'))')
define(`rand_t',`eval(randSeed^(randSeed>>13))') define(`random',
`define(`randSeed',eval((rand_t^(rand_t<<18))&0x7fffffff))randSeed')
define(`for',
`ifelse($#,0,``$0, `ifelse(eval($2<=$3),1, `pushdef(`$1',$2)$4`'popdef(`$1')$0(`$1',incr($2),$3,`$4')')')')
define(`set',`define(`$1[$2]',`$3')') define(`new',`set($1,size,0)') define(`get',`defn($1[$2])') define(`append',
`set($1,size,incr(get($1,size)))`'set($1,get($1,size),$2)')
define(`deck',
`new($1)for(`x',1,$2, `append(`$1',random)')')
define(`show',
`for(`x',1,get($1,size),`get($1,x)`'ifelse(x,get($1,size),`',`, ')')')
define(`swap',`set($1,$2,get($1,$4))`'set($1,$4,$3)') define(`shuffle',
`for(`x',1,get($1,size), `swap($1,x,get($1,x),eval(1+random%get($1,size)))')')
define(`inordern',
`ifelse(eval($2>=get($1,size)),1, 1, `ifelse(eval(get($1,$2)>get($1,incr($2))),1, 0, `inordern(`$1',incr($2))')')')
define(`inorder',`inordern($1,1)') define(`bogosort',
`ifelse(inorder(`$1'),0,`nope shuffle(`$1')`'bogosort(`$1')')')
divert
deck(`b',6) show(`b') bogosort(`b') show(`b')</lang>
Mathematica
<lang Mathematica>Bogosort[x_List] := Block[{t=x},While[!OrderedQ[t],t=RandomSample[x]]; t]
Bogosort[{1, 2, 6, 4, 0, -1, Pi, 3, 5}] => {-1, 0, 1, 2, 3, Pi, 4, 5, 6}</lang>
MATLAB
<lang MATLAB>function list = bogoSort(list)
while( ~issorted(list) ) %Check to see if it is sorted list = list( randperm(numel(list)) ); %Randomly sort the list end
end</lang>
Sample Output: <lang MATLAB>bogoSort([5 3 8 4 9 7 6 2 1])
ans =
1 2 3 4 5 6 7 8 9
</lang>
MAXScript
<lang maxscript>fn notSorted arr = (
if arr.count > 0 then ( local current = arr[1] for i in 2 to arr.count do ( if current > arr[i] then ( return true ) current = arr[i] ) ) false
)
fn randSort x y = (
random -1 1
)
fn shuffle arr = (
qsort arr randSort arr
)
fn bogosort arr = (
while notSorted arr do ( arr = shuffle arr ) arr
)</lang>
Modula-3
<lang modula3>MODULE Bogo EXPORTS Main;
IMPORT IO, Fmt, Random;
VAR a := ARRAY [1..5] OF INTEGER {1, 2, 3, 4, 5};
count := 0;
PROCEDURE Shuffle(VAR a: ARRAY OF INTEGER) =
VAR temp: INTEGER; BEGIN WITH rand = NEW(Random.Default).init() DO FOR i := FIRST(a) TO LAST(a) - 1 DO WITH j = rand.integer(i, LAST(a)) DO temp := a[i]; a[i] := a[j]; a[j] := temp; END; END; END; END Shuffle;
PROCEDURE Sorted(VAR a: ARRAY OF INTEGER): BOOLEAN =
BEGIN IF NUMBER(a) <= 1 THEN RETURN TRUE; END; FOR i := FIRST(a) + 1 TO LAST(a) DO IF (a[i] < a[i - 1]) THEN RETURN FALSE; END; END; RETURN TRUE; END Sorted;
BEGIN
Shuffle(a); WHILE NOT Sorted(a) DO Shuffle(a); INC(count); END; FOR i := FIRST(a) TO LAST(a) DO IO.PutInt(a[i]); IO.Put(" "); END; IO.Put("\nRequired " & Fmt.Int(count) & " shuffles\n");
END Bogo.</lang>
Nemerle
<lang Nemerle>using System; using System.Console; using Nemerle.Imperative;
module Bogosort {
public static Bogosort[T] (this x : array[T]) : void where T : IComparable { def rnd = Random(); def shuffle(a) { foreach (i in [0 .. (a.Length - 2)]) a[i] <-> a[(rnd.Next(i, a.Length))]; } def isSorted(b) { when (b.Length <= 1) return true; foreach (i in [1 .. (b.Length - 1)]) when (b[i].CompareTo(b[i - 1]) < 0) return false; true; } def loop() { unless (isSorted(x)) {shuffle(x); loop();}; }
loop() } Main() : void { def sortme = array[1, 5, 3, 6, 7, 3, 8, -2]; sortme.Bogosort(); foreach (i in sortme) Write($"$i "); }
}</lang>
NetRexx
<lang NetRexx>/* NetRexx */ options replace format comments java crossref savelog symbols nobinary
import java.util.List
method isSorted(list = List) private static returns boolean
if list.isEmpty then return isTrue
it = list.iterator last = Comparable it.next loop label i_ while it.hasNext current = Comparable it.next if last.compareTo(current) > 0 then return isFalse last = current end i_
return isTrue
method bogoSort(list = List) private static
loop label s_ while \isSorted(list) Collections.shuffle(list) end s_
return
method main(args = String[]) public constant
samples = [int 31, 41, 59, 26, 53, 58, 97, 93, 23, 84] alst = ArrayList(samples.length) loop iv = 0 to samples.length - 1 alst.add(Integer(samples[iv])) end iv
say 'unsorted:' alst.toString bogoSort(alst) say 'sorted: ' alst.toString
return
method isTrue public static returns boolean
return 1 == 1
method isFalse public static returns boolean
return \isTrue
</lang>
- Output
unsorted: [31, 41, 59, 26, 53, 58, 97, 93, 23, 84] sorted: [23, 26, 31, 41, 53, 58, 59, 84, 93, 97]
Oberon-2
<lang oberon2>MODULE Bogo;
IMPORT Out, Random;
VAR a: ARRAY 10 OF INTEGER;
PROCEDURE Init; VAR i: INTEGER; BEGIN FOR i := 0 TO LEN(a) - 1 DO a[i] := i + 1; END; END Init;
PROCEDURE Sorted(VAR a: ARRAY OF INTEGER): BOOLEAN; VAR i: INTEGER; BEGIN IF LEN(a) <= 1 THEN RETURN TRUE; END; FOR i := 1 TO LEN(a) - 1 DO IF (a[i] < a[i - 1]) THEN RETURN FALSE; END; END; RETURN TRUE; END Sorted;
PROCEDURE Shuffle*(VAR a: ARRAY OF INTEGER); VAR n, t, r: INTEGER; BEGIN FOR n := 0 TO LEN(a) - 1 DO r := Random.Roll(n); t := a[n]; a[n] := a[r]; a[r] := t; END; END Shuffle;
BEGIN
Init; Shuffle(a); WHILE ~Sorted(a) DO Shuffle(a); END; FOR i := 0 TO LEN(a) - 1 DO Out.Int(a[i], 0); Out.String(" "); END; Out.Ln;
END Bogo.</lang>
Init initializes the array as 1 thru 10, then it is shuffled, and then the while loop continually shuffles until Sorted returns true.
OCaml
<lang ocaml>let rec is_sorted comp = function
| e1 :: e2 :: r -> comp e1 e2 <= 0 && is_sorted comp (e2 :: r) | _ -> true
(* Fisher-Yates shuffle on lists; uses temp array *) let shuffle l =
let ar = Array.of_list l in for n = Array.length ar - 1 downto 1 do let k = Random.int (n+1) in let temp = ar.(k) in (* swap ar.(k) and ar.(n) *) ar.(k) <- ar.(n); ar.(n) <- temp done; Array.to_list ar
let rec bogosort li =
if is_sorted compare li then li else bogosort (shuffle li)</lang>
Example:
# bogosort [7;5;12;1;4;2;23;18] ;; - : int list = [1; 2; 4; 5; 7; 12; 18; 23]
Octave
<lang octave>function y = is_sorted(v)
y = true; for i = 2:length(v) if ( v(i-1) > v(i) ) y = false; return endif endfor
endfunction
function r = shuffle(v)
l = length(v); for i = 1:l t = v(i); r = unidrnd(l); v(i) = v(r); v(r) = t; endfor r = v;
endfunction
function s = bogosort(v)
while( !is_sorted(v) ) v = shuffle(v); endwhile s = v;
endfunction</lang>
<lang octave>n = [ 1, 10, 9, 7, 3, 0 ]; disp(bogosort(n));</lang>
Oz
We use an array because that made most sense for the Knuth Shuffle task. Usually you would use lists for stuff like this in Oz.
<lang oz>declare
proc {BogoSort Arr} for while:{Not {InOrder Arr}} do {Shuffle Arr} end end
fun {InOrder Arr} for I in {Array.low Arr}+1..{Array.high Arr}
return:Return default:true
do if Arr.(I-1) > Arr.I then {Return false} end end end
proc {Shuffle Arr} Low = {Array.low Arr} High = {Array.high Arr} in for I in High..Low;~1 do
J = Low + {OS.rand} mod (I - Low + 1)
OldI = Arr.I in
Arr.I := Arr.J
Arr.J := OldI end end
X = {Tuple.toArray unit(3 1 4 1 5 9 2 6 5)}
in
{BogoSort X} {Show {Array.toRecord unit X}}</lang>
PARI/GP
This implementation sorts 9 distinct elements in only 600 milliseconds. <lang parigp>bogosort(v)={
while(1, my(u=vecextract(v,numtoperm(#v,random((#v)!)))); for(i=2,#v,if(u[i]<u[i-1], next(2))); return(u) );
};</lang>
Pascal
<lang Pascal>program bogosort;
const
max = 5;
type
list = array [1..max] of integer;
{ Print a list } procedure printa(a: list); var
i: integer;
begin
for i := 1 to max do write(a[i], ' '); writeln
end;
{ Knuth shuffle } procedure shuffle(var a: list); var
i,k,tmp: integer;
begin
for i := max downto 2 do begin k := random(i) + 1; if (a[i] <> a[k]) then begin tmp := a[i]; a[i] := a[k]; a[k] := tmp end end
end;
{ Check for sorted list } function sorted(a: list): boolean; var
i: integer;
begin
sorted := True; for i := 2 to max do if (a[i - 1] > a[i]) then begin sorted := False; exit end
end;
{ Bogosort } procedure bogo(var a: list); var
i: integer;
begin
i := 1; randomize; write(i,': '); printa(a); while not sorted(a) do begin shuffle(a); i := i + 1; write(i,': '); printa(a) end
end;
{ Test and display } var
a: list; i: integer;
begin
for i := 1 to max do a[i] := (max + 1) - i; bogo(a);
end.</lang>
Sample Output:
1: 5 4 3 2 1 2: 3 5 4 1 2 . . . . . . 22: 3 2 1 5 4 23: 1 2 3 4 5
Perl
<lang perl>use List::Util qw(shuffle);
sub bogosort
{my @l = @_; @l = shuffle(@l) until in_order(@l); return @l;}
sub in_order
{my $last = shift; foreach (@_) {$_ >= $last or return 0; $last = $_;} return 1;}</lang>
Perl 6
<lang perl6>sub bogosort (@list is copy) {
@list .= pick(*) until [<=] @list; return @list;
}
my @nums = (^5).map: { rand }; say @nums.sort.Str eq @nums.&bogosort.Str ?? 'ok' !! 'not ok'; </lang>
PHP
<lang php>function bogosort($l) {
while (!in_order($l)) shuffle($l); return $l;
}
function in_order($l) {
for ($i = 1; $i < count($l); $i++) if ($l[$i] < $l[$i-1]) return FALSE; return TRUE;
}</lang>
PicoLisp
<lang PicoLisp>(de bogosort (Lst)
(loop (map '((L) (rot L (rand 1 (length L)))) Lst ) (T (apply <= Lst) Lst) ) )</lang>
Output:
: (bogosort (make (do 9 (link (rand 1 999))))) -> (1 167 183 282 524 556 638 891 902) : (bogosort (make (do 9 (link (rand 1 999))))) -> (20 51 117 229 671 848 883 948 978) : (bogosort (make (do 9 (link (rand 1 999))))) -> (1 21 72 263 391 476 794 840 878)
PowerShell
Shuffle taken from Knuth Shuffle <lang PowerShell>function shuffle ($a) {
$c = $a.Clone() # make copy to avoid clobbering $a 1..($c.Length - 1) | ForEach-Object { $i = Get-Random -Minimum $_ -Maximum $c.Length $c[$_-1],$c[$i] = $c[$i],$c[$_-1] $c[$_-1] # return newly-shuffled value } $c[-1] # last value
}
function isSorted( [Array] $data ) { $sorted = $true for( $i = 1; ( $i -lt $data.length ) -and $sorted; $i++ ) { $sorted = $data[ $i - 1 ] -le $data[ $i ] } $sorted }
function BogoSort ( [Array] $indata ) { $data = $indata.Clone() while( -not ( isSorted $data ) ) { $data = shuffle $indata } $data }
$l = 7; BogoSort ( 1..$l | ForEach-Object { $Rand = New-Object Random }{ $Rand.Next( 0, $l - 1 ) } )</lang>
PureBasic
<lang PureBasic>Procedure KnuthShuffle (Array a(1))
Protected i, Size = ArraySize(a()) For i = 0 To Size Swap a(i), a(Random(Size)) Next
EndProcedure
Procedure isSorted(Array a(1))
Protected i, Size = ArraySize(a()) For i = 1 To Size If a(i) < a(i - 1) ProcedureReturn #False EndIf Next ProcedureReturn #True
EndProcedure
Procedure BogoSort(Array a(1))
Protected Size = ArraySize(a()) + 1, iter While Not isSorted(a()) iter + 1 KnuthShuffle(a()) Wend MessageRequester("Results","Array of " + Str(Size) + " integers required " + Str(iter) + " shuffles To SORT.")
EndProcedure
Dim b(10) For i = 0 To 10
b(i) = Random(100)
Next
BogoSort(b())</lang> Sample output:
Array of 10 integers required 2766901 shuffles To SORT.
Python
<lang python>import random
def bogosort(l):
while not in_order(l): random.shuffle(l) return l
def in_order(l):
if not l: return True last = l[0] for x in l[1:]: if x < last: return False last = x return True</lang>
Alternative definition for in_order (Python 2.5) <lang python>def in_order(l):
return all( l[i] <= l[i+1] for i in xrange(0,len(l)-1))</lang>
An alternative implementation for Python 2.5 or later: <lang python>import random def bogosort(lst):
random.shuffle(lst) # must shuffle it first or it's a bug if lst was pre-sorted! :) while lst != sorted(lst): random.shuffle(lst) return lst</lang>
R
<lang R>bogosort <- function(x) {
is.sorted <- function(x) all(diff(x) >= 0) while(!is.sorted(x)) x <- sample(x) x
}
n <- c(1, 10, 9, 7, 3, 0) print(bogosort(n))</lang>
REXX
This is a modified bogo sort.
To verify the array is in order, a sequential search is performed.
When an number is found out of order, two random numbers between
the first number's position and the the position of the last number
checked are swapped.
A check is made to ensure that one number isn't being swapped with itself.
The search then starts over.
This is repeated as often as it takes to finally get the array in order.
<lang rexx>
/*REXX program to perform a type of bogo sort on an array. */
a.1= 0 /*this is really the 0th Berstel number... */ a.2= 0 a.3= 1 a.4= 2 a.5= 0 a.6= -4 a.7= 0 a.8= 16 a.9= 16
a.10= -32 a.11= -64 a.12= 64 a.13= 256 a.14= 0 a.15= -768 a.16= -512 a.17= 2048 a.18= 3072 a.19= -4096 a.20= -12288 a.21= 4096 a.22= 40960 a.23= 16384 a.24= -114688 a.25= -131072 a.26= 262144 a.27= 589824 a.28= -393216 a.29= -2097152 a.30= -262144 a.31= 6291456 a.32= 5242880 a.33= -15728640 a.34= -27262976 a.35= 29360128 a.36= 104857600 a.37= -16777216 a.38= -335544320 a.39= -184549376 a.40= 905969664
size=40 /*we have a list of two score Berstel numbers.*/ call tell 'un-bogoed'
do bogo=1
do j=1 for size _=a.j
do k=j+1 to size if a.k>=_ then iterate n=random(j,k) /*we have an num out of order.get rand*/ do forever; m=random(j,k) /*get another random number.*/ if m\==n then leave /*ensure we're not swapping the same #*/ end parse value a.n a.m with a.m a.n /*swap 2 random nums*/ iterate bogo end /*k*/
end /*j*/
leave end /*bogo*/
say 'number of bogo sorts performed =' bogo-1 call tell ' bogoed' exit
tell: say
say center(arg(1),40,'-')
do j=1 to size say arg(1) 'element'right(j,length(size))'='right(a.j,20) end
say return </lang> Output:
---------------un-bogoed---------------- un-bogoed element 1= 0 un-bogoed element 2= 0 un-bogoed element 3= 1 un-bogoed element 4= 2 un-bogoed element 5= 0 un-bogoed element 6= -4 un-bogoed element 7= 0 un-bogoed element 8= 16 un-bogoed element 9= 16 un-bogoed element10= -32 un-bogoed element11= -64 un-bogoed element12= 64 un-bogoed element13= 256 un-bogoed element14= 0 un-bogoed element15= -768 un-bogoed element16= -512 un-bogoed element17= 2048 un-bogoed element18= 3072 un-bogoed element19= -4096 un-bogoed element20= -12288 un-bogoed element21= 4096 un-bogoed element22= 40960 un-bogoed element23= 16384 un-bogoed element24= -114688 un-bogoed element25= -131072 un-bogoed element26= 262144 un-bogoed element27= 589824 un-bogoed element28= -393216 un-bogoed element29= -2097152 un-bogoed element30= -262144 un-bogoed element31= 6291456 un-bogoed element32= 5242880 un-bogoed element33= -15728640 un-bogoed element34= -27262976 un-bogoed element35= 29360128 un-bogoed element36= 104857600 un-bogoed element37= -16777216 un-bogoed element38= -335544320 un-bogoed element39= -184549376 un-bogoed element40= 905969664 number of bogo sorts performed = 3652 ---------------- bogoed---------------- bogoed element 1= -335544320 bogoed element 2= -184549376 bogoed element 3= -27262976 bogoed element 4= -16777216 bogoed element 5= -15728640 bogoed element 6= -2097152 bogoed element 7= -393216 bogoed element 8= -262144 bogoed element 9= -131072 bogoed element10= -114688 bogoed element11= -12288 bogoed element12= -4096 bogoed element13= -768 bogoed element14= -512 bogoed element15= -64 bogoed element16= -32 bogoed element17= -4 bogoed element18= 0 bogoed element19= 0 bogoed element20= 0 bogoed element21= 0 bogoed element22= 0 bogoed element23= 1 bogoed element24= 2 bogoed element25= 16 bogoed element26= 16 bogoed element27= 64 bogoed element28= 256 bogoed element29= 2048 bogoed element30= 3072 bogoed element31= 4096 bogoed element32= 16384 bogoed element33= 40960 bogoed element34= 262144 bogoed element35= 589824 bogoed element36= 5242880 bogoed element37= 6291456 bogoed element38= 29360128 bogoed element39= 104857600 bogoed element40= 905969664
More tests showed that:
number of bogo sorts performed = 2583 number of bogo sorts performed = 2376 number of bogo sorts performed = 1791 number of bogo sorts performed = 2537 number of bogo sorts performed = 1856 number of bogo sorts performed = 2339 number of bogo sorts performed = 2511 number of bogo sorts performed = 2652 number of bogo sorts performed = 1697 number of bogo sorts performed = 1782 number of bogo sorts performed = 2074 number of bogo sorts performed = 4017 number of bogo sorts performed = 2469 number of bogo sorts performed = 3707 number of bogo sorts performed = 1729 number of bogo sorts performed = 1705 number of bogo sorts performed = 4071
Ruby
<lang ruby>def shuffle(l)
l.sort_by { rand }
end
def bogosort(l)
l = shuffle(l) until in_order(l) l
end
def in_order(l)
(0..l.length-2).all? {|i| l[i] <= l[i+1] }
end</lang>
An alternative implementation:
<lang ruby>def shuffle(l)
l.sort_by { rand }
end
def bogosort(l)
l = shuffle(l) until l == l.sort l
end</lang>
<lang ruby>def in_order(l)
(0..l.length-2).all? {|i| l[i] <= l[i+1] }
end
def bogosort(l)
l.shuffle! until in_order(l) l
end</lang>
Scala
<lang scala>def isSorted(l: List[Int]) = l.iterator sliding 2 forall (s => s.head < s.last) def bogosort(l: List[Int]): List[Int] = if (isSorted(l)) l else bogosort(scala.util.Random.shuffle(l))</lang>
Smalltalk
This implementation uses closures rather than extending collections to provide a bogosort method. <lang smalltalk>Smalltalk at: #isItSorted put: [ :c |
|isit| isit := false. (2 to: (c size)) detect: [ :i | ( (c at: ( i - 1 )) > (c at: i) ) ] ifNone: [ isit := true ]. isit
]. Smalltalk at: #bogosort put: [ :c |
[ isItSorted value: c ] whileFalse: [ 1 to: (c size) do: [ :i | |r t| r := (Random between: 1 and: (c size)). t := (c at: i). c at: i put: (c at: r). c at: r put: t ] ]
].
|tobesorted| tobesorted := { 2 . 7 . 5 . 3 . 4 . 8 . 6 . 1 }. bogosort value: tobesorted. tobesorted displayNl.</lang>
SNOBOL4
<lang SNOBOL4>* Library for random() -include 'Random.sno'
- # String -> array
define('s2a(str,n)i') :(s2a_end)
s2a s2a = array(n); str = str ' ' sa1 str break(' ') . s2a span(' ') = :s(sa1)f(return) s2a_end
- # Array -> string
define('a2s(a)i') :(a2s_end)
a2s a2s = a2s a ' ' :s(a2s)f(return) a2s_end
- # Knuth shuffle in-place
define('shuffle(a)alen,n,k,tmp') :(shuffle_end)
shuffle n = alen = prototype(a); sh1 k = convert(random() * alen,'integer') + 1
eq(a<n>,a<k>) :s(sh2) tmp = a<n>; a<n> = a<k>; a<k> = tmp
sh2 n = gt(n,1) n - 1 :s(sh1)
shuffle = a :(return)
shuffle_end
- # sorted( ) predicate -> Succeed/Fail
define('sorted(a)alen,i') :(sorted_end)
sorted alen = prototype(a); i = 1 std1 i = lt(i,alen) i + 1 :f(return)
gt(a,a) :s(freturn)f(std1)
sorted_end
- # Bogosort
define('bogo(a)') :(bogo_end)
bogo output = (i = i + 1) ': ' a2s(a)
bogo = sorted(a) a :s(return) shuffle(a) :(bogo)
bogo_end
- # Test and display
bogo(s2a('5 4 3 2 1',5))
end</lang>
Sample Output:
1: 5 4 3 2 1 2: 2 1 4 3 5 . . . . . . 117: 3 2 1 5 4 118: 1 2 3 4 5
Tcl
<lang tcl>package require Tcl 8.5
proc shuffleInPlace {listName} {
upvar 1 $listName list set len [set len2 [llength $list]] for {set i 0} {$i < $len-1} {incr i; incr len2 -1} { # Pick cell to swap with set n [expr {int($i + $len2 * rand())}] # Perform swap set temp [lindex $list $i] lset list $i [lindex $list $n] lset list $n $temp }
} proc inOrder {list} {
set prev [lindex $list 0] foreach item [lrange $list 1 end] { if {$prev > $item} { return false } set prev $item } return true
} proc bogosort {list} {
while { ! [inOrder $list]} { shuffleInPlace list } return $list
}</lang>
TI-83 BASIC
Same IO as BozoSort (below).
:"BOGO" :L1→L2 :Lbl A :dim(L2)→A :For(B,1,dim(L2)-1) :randInt(1,A)→C :L2(C)→D :L2(A)→L2(C) :D→L2(A) :A-1→A :End :For(D,1,dim(L2)-1) :If L2(D)>L2(D+1) :Goto A :End :DelVar A :DelVar B :DelVar C :DelVar D :Return
This isn't a bogosort, but a bozosort. Store input into L1, run prgmSORTBOZO, outputs to L2
:L1→L2 :Lbl T :0→B :For(A,1,dim(L2)-1) :If L2(A)>L2(A+1) :1→B :End :If B=0 :Goto E :randInt(1,dim(L2))→C :randInt(1,dim(L2))→D :L2(C)→E :L2(C+1)→L2(C) :E→L2(C+1) :Goto T :Lbl E :DelVar A :DelVar B :DelVar C :DelVar D :DelVar E :Stop
Ursala
<lang Ursala>#import std
- import nat
shuffle = @iNX ~&l->r ^jrX/~&l ~&lK8PrC
bogosort = (not ordered nleq)-> shuffle
- cast %nL
example = bogosort <8,50,0,12,47,51></lang> output:
<0,8,12,47,50,51>
VBScript
Implementation
<lang vb>sub swap( byref a, byref b ) dim tmp tmp = a a = b b = tmp end sub
'knuth shuffle (I think) function shuffle( a ) dim i dim r randomize timer for i = lbound( a ) to ubound( a ) r = int( rnd * ( ubound( a ) + 1 ) ) if r <> i then swap a(i), a(r) end if next shuffle = a end function
function inOrder( a ) dim res dim i for i = 0 to ubound( a ) - 1 res = ( a(i) <= a(i+1) ) if res = false then exit for next inOrder = res end function</lang>
Invocation
<lang vb>dim a a = array(11, 1, 2, 3, 4, 4, 6, 7, 8)
dim t t = timer while not inorder( a ) shuffle a wend wscript.echo timer-t, "seconds" wscript.echo join( a, ", " )</lang>
A few outputs (timed)
10.34766 seconds 1, 2, 3, 4, 4, 6, 7, 8, 11 0.5039063 seconds 1, 2, 3, 4, 4, 6, 7, 8, 11 1.980469 seconds 1, 2, 3, 4, 4, 6, 7, 8, 11
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