快速排序-java实现

Posted 2021-02-12 yfy-

public class quickSort1 {
    public static void main(String[] args) {
        int[] num = {5, 23, -1, 3, 6, 4, 8, 1};
        new quickSort1().sort(num,0, num.length-1);
        for (int i = 0; i < num.length; i++) {
            System.out.print(num[i] + " ");
        }
    }
    public void sort(int[]num,int left, int right) {
        if (left > right)
            return;
        /*取数组的第一个值为基准*/
        int partition = num[left];
        int start = left;
        int end = right;
        /*定义两个指针，分别从数组的两端开始移动*/
        while (start!=end) {
            /*右端指针先走，直到找到小于基准的值*/
            while (start < end && num[end] >= partition) {
                end--;
            }
            /*左端指针后走，直到找到大于基准的值*/
            while (start < end && num[start] <= partition) {
                start++;
            }
            /*当左右指针还未相遇时就找到了目标，则交换位置*/
            if (start < end) {
                int i = num[start];
                num[start] = num[end];
                num[end] = i;
            }
        }
        //此时的left和right指针走到了一起
        //把基准数与该点交换位置
        num[left]=num[start];
        num[start]=partition;
        /*通过基准将数组分为两部分，继续排序*/
        sort(num,left, start - 1);
        sort(num,start + 1, right);
    }

}