Java Program for Recursive Insertion Sort

Insertion sort is a simple sorting algorithm that works the way we sort playing cards in our hands.Below is an iterative algorithm for insertion sort

Algorithm

// Sort an arr[] of size n
insertionSort(arr, n) 
    Loop from i = 1 to n-1.
       a) Pick element arr[i] and insert
          it into sorted sequence arr[0..i-1] 

Java

// Recursive Java program for insertion sort

import java.util.Arrays;

public class GFG
{
    // Recursive function to sort an array using
    // insertion sort
    static void insertionSortRecursive(int arr[], int n)
    {
        // Base case
        if (n <= 1)
            return;

        // Sort first n-1 elements
        insertionSortRecursive( arr, n-1 );

        // Insert last element at its correct position
        // in sorted array.
        int last = arr[n-1];
        int j = n-2;

        /* Move elements of arr[0..i-1], that are
          greater than key, to one position ahead
          of their current position */
        while (j >= 0 && arr[j] > last)
        {
            arr[j+1] = arr[j];
            j--;
        }
        arr[j+1] = last;
    }

    // Driver Method
    public static void main(String[] args)
    {
        int arr[] = {12, 11, 13, 5, 6};

        insertionSortRecursive(arr, arr.length);

        System.out.println(Arrays.toString(arr));
    }
}

Javascript

// Recursive JavaScript program for insertion sort

function insertionSortRecursive(arr, n) {
// Base case
if (n <= 1) {
return;
}

// Sort first n-1 elements
insertionSortRecursive(arr, n - 1);

// Insert last element at its correct position
// in sorted array.
const last = arr[n - 1];
let j = n - 2;

/* Move elements of arr[0..i-1], that are
greater than key, to one position ahead
of their current position */
while (j >= 0 && arr[j] > last) {
arr[j + 1] = arr[j];
j--;
}
arr[j + 1] = last;
}

// Driver Method
const arr = [12, 11, 13, 5, 6];

insertionSortRecursive(arr, arr.length);

console.log(arr);

Output:-

[5, 6, 11, 12, 13]

Time Complexity: O(n²)
Auxiliary Space: O(1)

Please refer complete article on Recursive Insertion Sort for more details!