排序--快速排序

public class Quicksort {
    public static void main(String[] args) {
        int [] arr={4,2,6,1,5,3,8,7,9,-1};
        ksSort(arr,0,arr.length-1);
        System.out.println(Arrays.toString(arr));
    }
    //递归排序
    private static void ksSort(int[] a, int low, int hight){
        if(low<hight){
            int mid=getMid(a,low,hight);//返回基准下标，基准左边的数都比基准小，右边大
            ksSort(a,low,mid-1);//递归排序基准左边的数
            ksSort(a,mid+1,hight);//递归排序基准右边的数
        }

    }
    //排序并且获取基准下标
    private static int getMid(int[] a, int low, int hight){
        int base=a[low];
        while (low!=hight){
            //循环一直找到右边比基准小的数然后和基准交换
            while (low<hight&&a[hight]>=base){
                hight--;
            }
            swap(a,low,hight);
            //循环一直找到左边比基准大的数然后和基准交换
            while (low<hight&&a[low]<=base){
                low++;
            }
            swap(a,low,hight);
        }
        return low;//返回low==hight时的下标，也是基准的下标
    }
    //交换
    private static void swap(int[] a,int low,int hight){
        int temp=a[low];
        a[low]=a[hight];
        a[hight]=temp;
    }
}