用Java语言实现快速排序

import java.util.Scanner;

public class QuickSort_2 {
    public static int [] quick_sort_1(int []a,int l,int r){
         if(l>=r){
             return null;
         }
         int i = l-1;
         int j = r+1;
         int x = a[l];
         while(ix);
             if(i