快排的递归与非递归实现（腾讯面试）

import java.util.*;
//快排的实现
public class quikSort{
	
   //(1)递归实现快速排序
   public static void quickSort(int[]s,int l,int r){
	 
	 if(l<r)
	 {
	 	 int i=l;
	     int j=r;
	     int pivot=s[l]; //取每个子数组的第一个数为基点
	     while(i<j)
	     {
           while(i<j&&s[j]>pivot) //从右向左
         	j--;
           if(j>i)
           {
            s[i++]=s[j];    
           }
          while(i<j&&s[i]<pivot)   //从左向右
            i++;
           if(i<j)
           {
         	s[j--]=s[i]; 
           }
	     }
	     s[i]=pivot;
         quickSort(s,l,i-1);
         quickSort(s,i+1,r);   
         
	 }
 
   }
   //非递归实现快速排序
 public static void NonRecQuickSort(int[] a,int start,int end) {
        LinkedList<Integer> stack = new LinkedList<Integer>();  //用栈模拟
        if(start < end) {
            stack.push(end);
            stack.push(start);
            while(!stack.isEmpty()) {
                int l = stack.pop();
                int r = stack.pop();
                int index = partition(a, l, r);
                if(l < index - 1) {
                    stack.push(index-1);
                    stack.push(l);
                }
                if(r > index + 1) {
                    stack.push(r);
                    stack.push(index+1);
                }
            }
        }
    }
    
  public static int partition(int[] a, int start, int end) {
        int pivot = a[start];
        while(start < end) {
            while(start < end && a[end] >= pivot)
                end--;
            a[start] = a[end];
            while(start < end && a[start] <= pivot)
                start++;
            a[end] = a[start];
        }
        a[start] = pivot;
        return start;
    }
   //打印数组的值
   public static void PrintArray(int[]arr)
   {
   	  for(int i=0;i<arr.length;i++)
   	  {
   	  	 System.out.print(arr[i]+" ");
   	  }
   	   System.out.println();
 
   }
   public static void main(String[]args)
   {
       int[]arr={3,6,5,2,5,4,3,8};
       PrintArray(arr);
       //quickSort(arr,0,arr.length-1);
       NonRecQuickSort(arr,0,arr.length-1);
       PrintArray(arr);
   }
 }