Day_39_MergeSort.java

package com.TrX;

import java.util.Arrays;
import java.util.Scanner;

public class Day_39_MergeSort {
    void merge(int array[], int p, int q, int r) {

        int n1 = q - p + 1;
        int n2 = r - q;

        int L[] = new int[n1];
        int M[] = new int[n2];

        for (int i = 0; i < n1; i++)
            L[i] = array[p + i];
        for (int j = 0; j < n2; j++)
            M[j] = array[q + 1 + j];

        int i, j, k;
        i = 0;
        j = 0;
        k = p;


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


        while (i < n1) {
            array[k] = L[i];
            i++;
            k++;
        }

        while (j < n2) {
            array[k] = M[j];
            j++;
            k++;
        }
    }

    void mergeSort(int array[], int left, int right) {
        if (left < right) {

            int mid = (left + right) / 2;
            mergeSort(array, left, mid);
            mergeSort(array, mid + 1, right);
            merge(array, left, mid, right);
        }
    }

    public static void main(String args[]) {
        Day_39_MergeSort ob = new Day_39_MergeSort();
        System.out.println("Enter the size of array");
        Scanner s=new Scanner(System.in);
        int size=s.nextInt();
        int [] array=new int[size];
        for(int i=0;i<size;i++){
            System.out.println("enter "+i+"th element");
            array[i]=s.nextInt();
        }
        ob.mergeSort(array, 0, array.length - 1);
        System.out.println(Arrays.toString(array));
    }
}