BogoSort

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.

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 known in which step the resultant permutation will come out to be sorted.

CODE:

# Python program for implementation of Bogo Sort 
import random 
  
# Sorts array a[0..n-1] using Bogo sort 
def bogoSort(a): 
    n = len(a) 
    while (is_sorted(a)== False): 
        shuffle(a) 
  
# To check if array is sorted or not 
def 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 permuatation of the array 
def 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 above 
a = [3, 2, 4, 1, 0, 5] 
bogoSort(a) 
print("Sorted array :") 
for i in range(len(a)): 
    print ("%d" %a[i]), 

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)