BogoSort or Permutation Sort - GeeksforGeeks

26 Jan, 2022
BogoSort also known as permutation sort, stupid sort, slow sort, shotgun sort or monkey sort is a particularly ineffective algorithm based on generate and test paradigm. The algorithm successively generates permutations of its input until it finds one that is sorted.(Wiki)For example, if bogosort is used to sort a deck of cards, it would consist of checking if the deck were in order, and if it were not, one would throw the deck into the air, pick the cards up at random, and repeat the process until the deck is sorted.PseudoCode:
while not Sorted(list) do
    shuffle (list)
done

Example:
Let us consider an example array ( 3 2 5 1 0 4 )4 5 0 3 2 1 (1st shuffling)4 1 3 2 5 0 (2ndshuffling)1 0 3 2 5 4 (3rd shuffling)3 1 0 2 4 5 (4th shuffling)1 4 5 0 3 2 (5th shuffling)...0 1 2 3 4 5 (nth shuffling)—— Sorted Array
Here, n is unknown because algorithm doesn’t know in which step the resultant permutation will come out to be sorted.
C++
Java
Python
C#
// C++ implementation of Bogo Sort#include<bits/stdc++.h>using namespace std;  // To check if array is sorted or notbool isSorted(int a[], int n){    while ( --n > 1 )        if (a[n] < a[n-1])            return false;    return true;}  // To generate permutation of the arrayvoid shuffle(int a[], int n){    for (int i=0; i < n; i++)        swap(a[i], a[rand()%n]);}  // Sorts array a[0..n-1] using Bogo sortvoid bogosort(int a[], int n){    // if array is not sorted then shuffle    // the array again    while ( !isSorted(a, n) )        shuffle(a, n);}  // prints the arrayvoid printArray(int a[], int n){    for (int i=0; i<n; i++)        printf("%d ", a[i]);    printf("\n");}  // Driver codeint main(){    int a[] = {3, 2, 5, 1, 0, 4};    int n = sizeof a/sizeof a[0];    bogosort(a, n);    printf("Sorted array :\n");    printArray(a,n);    return 0;}
// Java Program to implement BogoSortpublic class BogoSort{    // Sorts array a[0..n-1] using Bogo sort    void bogoSort(int[] a)    {        // if array is not sorted then shuffle the        // array again        while (isSorted(a) == false)            shuffle(a);    }      // To generate permutation of the array    void shuffle(int[] a)    {         // Math.random() returns a double positive         // value, greater than or equal to 0.0 and         // less than 1.0.         for (int i=1; i <= n; i++)             swap(a, i, (int)(Math.random()*i));    }      // Swapping 2 elements    void swap(int[] a, int i, int j)    {        int temp = a[i];        a[i] = a[j];        a[j] = temp;    }      // To check if array is sorted or not    boolean isSorted(int[] a)    {        for (int i=1; i<a.length; i++)            if (a[i] < a[i-1])                return false;        return true;    }      // Prints the array    void printArray(int[] arr)    {        for (int i=0; i<arr.length; i++)            System.out.print(arr[i] + " ");        System.out.println();    }      public static void main(String[] args)    {        //Enter array to be sorted here        int[] a = {3, 2, 5, 1, 0, 4};        BogoSort ob = new BogoSort();          ob.bogoSort(a);          System.out.print("Sorted array: ");        ob.printArray(a);    }}
# Python program for implementation of Bogo Sortimport random  # Sorts array a[0..n-1] using Bogo sortdef bogoSort(a):    n = len(a)    while (is_sorted(a)== False):        shuffle(a)  # To check if array is sorted or notdef is_sorted(a):    n = len(a)    for i in range(0, n-1):        if (a[i] > a[i+1] ):            return False    return True  # To generate permutation of the arraydef shuffle(a):    n = len(a)    for i in range (0,n):        r = random.randint(0,n-1)        a[i], a[r] = a[r], a[i]  # Driver code to test abovea = [3, 2, 4, 1, 0, 5]bogoSort(a)print("Sorted array :")for i in range(len(a)):    print ("%d" %a[i]),
// C# implementation of Bogo Sortusing System;     class GFG {     // To Swap two given numbers    static void Swap<T>(ref T lhs, ref T rhs)    {        T temp;        temp = lhs;        lhs = rhs;        rhs = temp;    }          // To check if array is sorted or not     public static bool isSorted(int[] a, int n)     {         int i = 0;        while(i<n-1)        {            if(a[i]>a[i+1])                return false;            i++;        }        return true;    }             // To generate permutation of the array     public static void shuffle(int[] a, int n)     {         Random rnd = new Random();        for (int i=0; i < n; i++)             Swap(ref a[i], ref a[rnd.Next(0,n)]);     }             // Sorts array a[0..n-1] using Bogo sort     public static void bogosort(int[] a, int n)     {         // if array is not sorted then shuffle         // the array again         while ( !isSorted(a, n) )             shuffle(a, n);     }             // prints the array     public static void printArray(int[] a, int n)     {         for (int i=0; i<n; i++)             Console.Write(a[i] + " ");         Console.Write("\n");     }           // Driver code    static void Main()     {         int[] a = {3, 2, 5, 1, 0, 4};         int n = a.Length;         bogosort(a, n);         Console.Write("Sorted array :\n");         printArray(a,n);     }    //This code is contributed by DrRoot_}
Output:
Sorted array :
0 1 2 3 4 5 

Time Complexity:
Worst Case : O(∞) (since this algorithm has no upper bound)
Average Case: O(n*n!)
Best Case : O(n)(when array given is already sorted)
Auxiliary Space: O(1)
This article is contributed by Rahul Agrawal . If you like GeeksforGeeks and would like to contribute, you can also write an article using contribute.geeksforgeeks.org or mail your article to contribute@geeksforgeeks.org. See your article appearing on the GeeksforGeeks main page and help other Geeks.
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