# Stooge Sort

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.

## Recommended: Please try your approach on {IDE} first, before moving on to the solution.

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```

## 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)>
```

Output:

```1 2 3 4 5
```

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

T(n) = 3T(3n/2) + Θ(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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