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Stooge Sort
  • Difficulty Level : Hard
  • Last Updated : 04 Apr, 2018

The Stooge sort is a recursive sorting algorithm. It is defined as below (for ascending order sorting).

Step 1 : If value at index 0 is greater than
         value at last index, swap them.
Step 2:  Recursively, 
       a) Stooge sort the initial 2/3rd of the array.
       b) Stooge sort the last 2/3rd of the array.
       c) Stooge sort the initial 2/3rd again to confirm.

NOTE: Always take the ceil of ((2/3)*N) for selecting elements.


Illustration:

Input :   2 4 5 3 1
Output : 1 2 3 4 5
Explanation:
Initially, swap 2 and 1 following above step 1.
          1 4 5 3 2
          Now, recursively sort initial 2/3rd of the elements.
          1 4 5 3 2
          1 3 4 5 2 
          Then, recursively sort last 2/3rd of the elements.
          1 3 4 5 2
          1 2 3 4 5
          Again, sort the initial 2/3rd of the elements to confirm final data is sorted.
          1 2 3 4 5

stooge_sort



C++




// C++ code to implement stooge sort
#include <iostream>
using namespace std;
  
// Function to implement stooge sort
void stoogesort(int arr[], int l, int h)
{
    if (l >= h)
        return;
  
    // If first element is smaller than last,
    // swap them
    if (arr[l] > arr[h])
        swap(arr[l], arr[h]);
  
    // If there are more than 2 elements in
    // the array
    if (h - l + 1 > 2) {
        int t = (h - l + 1) / 3;
  
        // Recursively sort first 2/3 elements
        stoogesort(arr, l, h - t);
  
        // Recursively sort last 2/3 elements
        stoogesort(arr, l + t, h);
  
        // Recursively sort first 2/3 elements
        // again to confirm
        stoogesort(arr, l, h - t);
    }
}
  
// Driver Code
int main()
{
    int arr[] = { 2, 4, 5, 3, 1 };
    int n = sizeof(arr) / sizeof(arr[0]);
  
    // Calling Stooge Sort function to sort
    // the array
    stoogesort(arr, 0, n - 1);
  
    // Display the sorted array
    for (int i = 0; i < n; i++)
        cout << arr[i] << " ";
  
    return 0;
}

Java




// Java program to implement stooge sort
import java.io.*;
  
public class stooge {
    // Function to implement stooge sort
    static void stoogesort(int arr[], int l, int h)
    {
        if (l >= h)
            return;
  
        // If first element is smaller
        // than last, swap them
        if (arr[l] > arr[h]) {
            int t = arr[l];
            arr[l] = arr[h];
            arr[h] = t;
        }
  
        // If there are more than 2 elements in
        // the array
        if (h - l + 1 > 2) {
            int t = (h - l + 1) / 3;
  
            // Recursively sort first 2/3 elements
            stoogesort(arr, l, h - t);
  
            // Recursively sort last 2/3 elements
            stoogesort(arr, l + t, h);
  
            // Recursively sort first 2/3 elements
            // again to confirm
            stoogesort(arr, l, h - t);
        }
    }
  
    // Driver Code
    public static void main(String args[])
    {
        int arr[] = { 2, 4, 5, 3, 1 };
        int n = arr.length;
  
        stoogesort(arr, 0, n - 1);
  
        for (int i = 0; i < n; i++)
            System.out.print(arr[i] + " ");
    }
}
// Code Contributed by Mohit Gupta_OMG <(0_o)>

Python3




# Python program to implement stooge sort
  
def stoogesort(arr, l, h):
    if l >= h:
        return
   
    # If first element is smaller
    # than last, swap them
    if arr[l]>arr[h]:
        t = arr[l]
        arr[l] = arr[h]
        arr[h] = t
   
    # If there are more than 2 elements in
    # the array
    if h-l + 1 > 2:
        t = (int)((h-l + 1)/3)
   
        # Recursively sort first 2 / 3 elements
        stoogesort(arr, l, (h-t))
   
        # Recursively sort last 2 / 3 elements
        stoogesort(arr, l + t, (h))
   
        # Recursively sort first 2 / 3 elements
        # again to confirm
        stoogesort(arr, l, (h-t))
   
  
# deriver 
arr = [2, 4, 5, 3, 1]
n = len(arr)
  
stoogesort(arr, 0, n-1)
   
for i in range(0, n):
    print(arr[i], end = ' ')
  
# Code Contributed by Mohit Gupta_OMG <(0_o)>

C#




// C# program to implement stooge sort
using System;
  
class GFG {
      
    // Function to implement stooge sort
    static void stoogesort(int[] arr,
                            int l, int h)
    {
        if (l >= h)
            return;
  
        // If first element is smaller
        // than last, swap them
        if (arr[l] > arr[h]) {
            int t = arr[l];
            arr[l] = arr[h];
            arr[h] = t;
        }
  
        // If there are more than 2 
        // elements in the array
        if (h - l + 1 > 2) {
            int t = (h - l + 1) / 3;
  
            // Recursively sort first 
            // 2/3 elements
            stoogesort(arr, l, h - t);
  
            // Recursively sort last
            // 2/3 elements
            stoogesort(arr, l + t, h);
  
            // Recursively sort first 
            // 2/3 elements again to 
            // confirm
            stoogesort(arr, l, h - t);
        }
    }
  
    // Driver Code
    public static void Main()
    {
        int[] arr = { 2, 4, 5, 3, 1 };
        int n = arr.Length;
  
        // Calling Stooge Sort function
        // to sort the array
        stoogesort(arr, 0, n - 1);
  
        // Display the sorted array
        for (int i = 0; i < n; i++)
            Console.Write(arr[i] + " ");
    }
}
  
// This code is contributed by Sam007.

Output:

1 2 3 4 5 

The running time complexity of stooge sort can be written as,

T(n) = 3T(3n/2) + ?(1)

Solution of above recurrence is O(n(log3/log1.5)) = O(n2.709), hence it is slower than even bubble sort(n^2).

Reference:
Wikipedia

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