快速排序

快速排序是基于冒泡排序的，同属于交换排序。思路是选择一个基值，从前后两端小于此值的放在左边，大于这个值的防在右边。然后递归，基值左边和右边再分别进行此操作。

package exchenge;

import java.util.Arrays;
public class Quike {
	public static void main(String[] args) {
		int[] A={7,8,9,6,4,98,2,1,11,11,21,34,43,54,11,45,67,76,5};
		quicksort(A, 0, A.length-1);
		System.out.println(Arrays.toString(A));
	}
	public static int partition(int[] A,int low,int high){
		int b=A[low];//寄存在b中 
		while(low<high){//从两端逼近，直到相遇停止
			while(low<high&&A[high]>=b){//low和high下标下的内容交换
				high--;
			}
			A[low]=A[high];
			while(low<high&&A[low]<=b){
				low++;
			}
			A[high]=A[low];
		}
		A[low]=b;//将b中寄存的数放入A[low],此时low=high
		return low;
	}
	public static void quicksort(int[] A,int low,int high){
		if(low<high){
			int b=partition(A, low, high);
			quicksort(A, low, b-1);
			quicksort(A, b+1, high);
		}
	}
}