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);
        double[] num = new double[4];
        int[] visit = new int[4];
        boolean flag = false;
        for(int i=0; i<4; i++){
            num[i] = (double)in.nextInt();
            visit[i] = 0;
        }
        for(int i=0; i<4; i++){
            visit[i] = 1;
            if(dfs(num,visit,num[i])){
                flag = true;
                break;
            }
        }
        System.out.print(flag);
    }
    public static boolean dfs(double[] num, int[] visit, double res){
        if(res == (double)24){
            return true;
        }
        for(int i=0; i<4; i++){
            if(visit[i] == 0){
                visit[i] = 1;//标记已使用
                if(dfs(num, visit, res + num[i])
                || dfs(num, visit, res - num[i])
                || dfs(num, visit, res * num[i])
                || dfs(num, visit, res / num[i])){
                    return true;
                }
                visit[i] = 0;//回溯
            }    
        }
        return false;
    }
}