归并排序Java实现

归并排序

public class mJava {
    public static int merge(int[] arr, int L, int m, int r) {
        int[] help = new int[r - L + 1];
        int i = 0;
        int p1 = L;
        int p2 = m + 1;
        int res = 0;
        while (p1 <= m && p2 <= r) {
           
            help[i++] = arr[p1] < arr[p2] ? arr[p1++] : arr[p2++];
        }
        while (p1 <= m) {
            help[i++] = arr[p1++];
        }
        while (p2 <= r) {
            help[i++] = arr[p2++];
        }
        for ( i = 0; i < help.length ; i++ ) {
            arr[L + i] = help[i];
        }
        return res;
    }

    public static void process(int[] arr, int l, int r) {
        if (l == r) {
          return;
        }
        int mid = l + ( ( r - l ) >> 1 );
         process(arr, l, mid) ; process(arr, mid + 1, r) ; merge(arr, l, mid, r);
    }
    public static void main(String[] args){
        int []a= new int[]{2, 5, 6, 2, 4, 8, 9, 6};
        process(a,0,a.length-1);
        for ( int i=0;i< a.length;++i ){
            System.out.println(a[i]);
        }
    }


}