MergeSort_main

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package algorithm;

/**
 *
 * @author acer
 */
public class mergeSort {

    public static int [] a={2,4,1,6,8,5,3,7};

    public static void main(String[] args) {



        mergeSort(a,0,a.length-1);
        System.out.println();
        print(a);


    }
    public static void mergeSort(int []a,int p,int r){
    if(p<r){
    int q=(p+r)/2;
    mergeSort(a,p,q);
    mergeSort(a,q+1,r);
    merge(a,p,q,r);
    }
    }

    public static void print(int [] arr){
         for(int n:arr){
           System.out.print(n+" ");
       }
         System.out.println();
    }

    public static void merge(int [] a,int p,int q, int r){

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

        int[]l=new int[n1+1];
        int [] ri=new int[n2+1];

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

        for(int i=0;i<n2;i++){
            ri[i]=a[q+1+i];

        }
        System.out.println();

        print(l);

        print(ri);


        int i=0;
        int j=0;

        l[n1]=2222222;
        ri[n2]=2222222;

    for(int k=p;k<=r;k++){

           if(l[i]<=ri[j]){
               a[k]=l[i];
               i++;

           }
           else{
               a[k]=ri[j];
               j++;

           }

       }




    }
}