Java Program for Iterative Merge Sort

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Following is a typical recursive implementation of Merge Sort that uses last element as pivot.

Java

// Recursive Java Program for merge sort 
  
import java.util.Arrays; 
public class GFG 
{ 
    public static void mergeSort(int[] array) 
    { 
        if(array == null) 
        { 
            return; 
        } 
  
        if(array.length > 1) 
        { 
            int mid = array.length / 2; 
  
            // Split left part 
            int[] left = new int[mid]; 
            for(int i = 0; i < mid; i++) 
            { 
                left[i] = array[i]; 
            } 
              
            // Split right part 
            int[] right = new int[array.length - mid]; 
            for(int i = mid; i < array.length; i++) 
            { 
                right[i - mid] = array[i]; 
            } 
            mergeSort(left); 
            mergeSort(right); 
  
            int i = 0; 
            int j = 0; 
            int k = 0; 
  
            // Merge left and right arrays 
            while(i < left.length && j < right.length) 
            { 
                if(left[i] < right[j]) 
                { 
                    array[k] = left[i]; 
                    i++; 
                } 
                else
                { 
                    array[k] = right[j]; 
                    j++; 
                } 
                k++; 
            } 
            // Collect remaining elements 
            while(i < left.length) 
            { 
                array[k] = left[i]; 
                i++; 
                k++; 
            } 
            while(j < right.length) 
            { 
                array[k] = right[j]; 
                j++; 
                k++; 
            } 
        } 
    } 
    // Driver program to test above functions. 
    public static void main(String[] args) 
    { 
        int arr[] = {12, 11, 13, 5, 6, 7}; 
        int i=0; 
        System.out.println("Given array is"); 
  
        for(i=0; i<arr.length; i++) 
            System.out.print(arr[i]+" "); 
  
        mergeSort(arr); 
  
        System.out.println("\n"); 
        System.out.println("Sorted array is"); 
  
        for(i=0; i<arr.length; i++) 
            System.out.print(arr[i]+" "); 
    } 
} 
  
// Code Contributed by Mohit Gupta_OMG 

Time Complexity: O(n*log(n))
Auxiliary Space: O(n)

Please refer complete article on Iterative Merge Sort for more details!

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