题解 | #24点游戏算法#

import java.util.Scanner;

// 注意类名必须为 Main, 不要有任何 package xxx 信息
public class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextInt()) { // 注意 while 处理多个 case
            int[] nums = new int[4];
            for(int i=0 ; i<4 ; ++i){
                nums[i] = in.nextInt();
            }
            boolean[] visited = new boolean[4];
            boolean flag = false;

            for(int i=0 ; i<4 ; ++i){
                visited[i] = true;
                if(dfs(nums, visited, nums[i])){
                    flag = true;
                }
            }
            System.out.println(flag);
        }
    }

    public static boolean dfs(int[] nums, boolean[] visited, int value){
        for(int i=0 ; i<4 ; ++i){
            if(!visited[i]){
                visited[i] = true;
                if(dfs(nums, visited, value+nums[i]) || dfs(nums, visited, value-nums[i]) || dfs(nums, visited, value*nums[i]) || dfs(nums, visited, value/nums[i])){
                    return true;
                }
                visited[i] = false; //不满足情况，则重新回溯
            }
        }
        if(value == 24){
            return true;
        }
        return false;
    } 
}