使用递归算法实现冒泡：

 

package com.nami.algorithm.study.day06;

import java.util.Arrays;

/**
 * beyond u self and trust u self.
 *
 * @Author: lbc
 * @Date: 2023-09-05 15:36
 * @email: 594599620@qq.com
 * @Description: keep coding
 */
public class BubbleSort2 {

//    public static void sort(int[] target, int num) {
//        if (num == 0) {
//            return;
//        }
//        bubble(target, num-1);
//
//        sort(target, num-1);
//    }
//
//    private static void bubble(int[] target, int j) {
//        for (int i = 0; i < j; i++) {
//            if (target[i] > target[i + 1]) {
//                int temp = target[i];
//                target[i] = target[i+1];
//                target[i+1] = temp;
//            }
//        }
//    }

    public static void sort(int[] target) {
        bubble(target, target.length -1 );
    }

    private static void bubble(int[] target, int j) {
        if (j == 0) {
            return;
        }

        for (int i = 0; i < j; i++) {
            if (target[i] > target[i + 1]) {
                int temp = target[i];
                target[i] = target[i+1];
                target[i+1] = temp;
            }
        }
        bubble(target, j - 1);
    }


    public static void main(String[] args) {
        int[] test = new int[]{1, 54, 234, 675, 32432, 23, 78, 459, 354, 9, 344, 22, 46, 85, 236, 3278, 245, 83, 154, 2, 1, 34, 73, 23};
        int[] test2= new int[] {2,4,7,3,2,1};
//        sort(test, test.length);
        sort(test2);
        System.out.println(Arrays.toString(test2));
    }


}

优化数组稳定得情况, 减少无意义遍历，新增参数x, 标识是否发生了挪动，递归时使用x索引，非常巧妙。递归妙

package com.nami.algorithm.study.day06;

import java.util.Arrays;

/**
 * beyond u self and trust u self.
 *
 * @Author: lbc
 * @Date: 2023-09-05 15:36
 * @email: 594599620@qq.com
 * @Description: keep coding
 */
public class BubbleSort {
 
    public static void sort(int[] target) {
        bubble(target, target.length -1 );
    }

    private static void bubble(int[] target, int j) {
        if (j == 0) {
            return;
        }

        // 变换标识 索引i
        int x = 0;

        for (int i = 0; i < j; i++) {
            if (target[i] > target[i + 1]) {
                int temp = target[i];
                target[i] = target[i+1];
                target[i+1] = temp;
                x = i;
            }
        }
        bubble(target, x);
    }

    public static void main(String[] args) {
        int[] test = new int[]{1, 54, 234, 675, 32432, 23, 78, 459, 354, 9, 344, 22, 46, 85, 236, 3278, 245, 83, 154, 2, 1, 34, 73, 23};
        int[] test2= new int[] {2,4,7,3,2,1};
//        sort(test, test.length);
        sort(test2);
        System.out.println(Arrays.toString(test2));
    }


}