MergeSort.java

import java.util.*;
public class MergeSort {

	void mergesort(int arr[], int l, int m, int r)

	{
	int n1 = m - l + 1;
	int n2 = r - m;
	int L[] = new int[n1];
	int R[] = new int[n2];

	for (int i = 0; i < n1; ++i) {
		L[i] = arr[l + i];
	}

	for (int j = 0; j < n2; ++j) {
		R[j] = arr[m + 1 + j];
	}	
	int i = 0, j = 0;
	int k = l;

	while (i < n1 && j < n2) {
		
		if (L[i] <= R[j]) {
			arr[k] = L[i];
			i++;
			}
		else {
			arr[k] = R[j];
			j++;
			}
		k++;

	}
	while (i < n1) {
		
		arr[k] = L[i];
		i++;
		k++;
	}
	while (j < n2) {
		arr[k] = R[j];
		j++;
		k++;
		}

	}
	void sort(int arr[], int l, int r)

	{
		if (l < r) {
			int m = l + (r - l) / 2;
			sort(arr, l, m);
			sort(arr, m + 1, r);
			mergesort(arr, l, m, r);
			}

	}

	static void printArray(int arr[])

	{

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

	}
	public static void main(String args[])
	{
	      int i, n, x, arr[];

	      Scanner s = new Scanner(System.in);
	      System.out.println("Enter no. of elements in aray:");
	      n = s.nextInt(); 

	      arr = new int[n];

	      System.out.println("Enter " + n + " integers:");

	      for (i = 0;i<n; i++)
	          arr[i] = s.nextInt();

		MergeSort ob = new MergeSort();
	      ob.sort(arr, 0, arr.length - 1);
	      System.out.println("\nSorted array is");

	printArray(arr);
	}

}