MergeSort.java

package sorting;

import java.util.ArrayList;
public class MergeSort {
    static void merge(int arr[],int low, int mid, int high){
        ArrayList<Integer> temp = new ArrayList<>(); // temporary array
        int left = low;      // starting index of left half of arr
        int right = mid + 1;   // starting index of right half of arr

        //storing elements in the temporary array in a sorted manner//

        while (left <= mid && right <= high) {
            if (arr[left] <= arr[right]) {
                temp.add(arr[left]);
                left++;
            } else {
                temp.add(arr[right]);
                right++;
            }
        }

        // if elements on the left half are still left //

        while (left <= mid) {
            temp.add(arr[left]);
            left++;
        }

        //  if elements on the right half are still left //
        while (right <= high) {
            temp.add(arr[right]);
            right++;
        }

        // transfering all elements from temporary to arr //
        for (int i = low; i <= high; i++) {
            arr[i] = temp.get(i - low);
        }
    }

    static void mergeSort(int arr[],int low, int high){
        if(low>=high)return;
        int mid = (high+low)/2;
        mergeSort(arr, low, mid); //left half
        mergeSort(arr,mid+1,high); //right half
        merge(arr,low,mid,high); //merging sorted halves
    }



    public static void main(String[] args) {
        int arr[] = { 9, 4, 7, 6, 3, 1, 5 };

        mergeSort(arr,0,arr.length-1);
        for (int i = 0; i < arr.length; i++) {
            System.out.print(arr[i] + " ");
        }

    }
}