mergeSort.java

import java.util.Arrays;

public class mergeSort {
    public static void main(String[] args) {
    int[] arr = {5,32,12,31,2};
     mergeSortInp(arr,0,arr.length);
        System.out.println(Arrays.toString(arr));
    }

    static int[] mergesort(int[] arr) {
        if (arr.length == 1) {
            return arr;
        }
        int mid = arr.length / 2;
        int[] left = mergesort(Arrays.copyOfRange(arr, 0, mid));
        int[] right = mergesort(Arrays.copyOfRange(arr, mid, arr.length));
        return merge(left, right);
    }

    private static int[] merge(int[] first, int[] second) {
        int[] mix = new int[first.length + second.length];
        int i = 0;

        int j = 0;
        int k = 0;
        while (i < first.length && j < second.length) {
            if (first[i] < second[j]) {
                mix[k] = first[i];
                i++;
            } else {
                mix[k] = second[j];
                j++;
            }
            k++;
        }
        while (i < first.length) {
            mix[k] = first[i];
            i++;
            k++;
        }
        while (j < second.length) {
            mix[k] = second[j];
            j++;
            k++;
        }
        return mix;
    }

    static void mergeSortInp(int[] arr, int s, int e) {
        if (e-s == 1) {
            return;
        }
        int mid = (s+e)/2;
        mergeSortInp(arr,s,mid);
         mergeSortInp(arr,mid,e);
         mergeInp(arr,s,mid,e);

    }
    private static void mergeInp(int[] arr,int s,int m,int e){
        int[] mix = new int[e-s];
        int i =s;
        int j=m;
        int k=0;
        while(i<m&&j<e){
            if(arr[i]<arr[j]){
                mix[k]=arr[i];
                i++;
            }else{
                mix[k]=arr[j];
                j++;
            }
            k++;
        }
        while(i<m){
            mix[k]=arr[i];
            i++;
            k++;
        }
        while(j<e){
            mix[k]=arr[j];
            j++;
            k++;
        }
        System.arraycopy(mix, 0, arr, s + 0, mix.length);

    }

}