Mergesort.java

import java.util.Scanner;

public class Mergesort {
    public static void conquer(int arr[], int si, int mid, int ei){
        int merged[]=new int[ei-si+1];

        int idx1 = si;
        int idx2 = mid+1;
        int x = 0;

        while(idx1 <= mid && idx2 <= ei){
            if(arr[idx1] <= arr[idx2]) {
                merged[x++] = arr[idx1++];
            } else{
                merged[x++] = arr[idx2++];
            }
        }
        while(idx1 <= mid){
             merged[x++] = arr[idx1++];
        }
        while(idx2 <= ei){
             merged[x++] = arr[idx2++];
        }

        for(int i=0, j=si; i<merged.length; i++, j++){
            arr[j]=merged[i];
        }
    }
    public static void divide(int arr[],int si,int ei){
        if(si>=ei){
            return; 
        }
        int mid = si + (ei-si)/2;
        divide(arr, si, mid);
        divide(arr, mid+1, ei);
        conquer(arr, si, mid, ei);
    }

    public static void main(String args[]) {
        Scanner sc = new Scanner(System.in);

        System.out.print("Enter the number of elements: ");
        int n = sc.nextInt();

        int arr[] = new int[n];
        System.out.println("Enter " + n + " elements:");

        for (int i = 0; i < n; i++) {
            arr[i] = sc.nextInt();
        }

        divide(arr, 0, n - 1);

        System.out.println("Sorted array:");
        for (int i = 0; i < n; i++) {
            System.out.print(arr[i] + " ");
        }

        System.out.println();
        sc.close();
    }
}