题解 | #24点游戏算法#DFS暴力求解24点游戏

import java.util.Scanner;
public class Main {
    public static boolean[] visited = new boolean[4];
    public static int[] nums = new int[4];
    public static boolean flag = false;
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while (in.hasNext()) {
            for(int i=0;i<4;i++){
                nums[i] = in.nextInt();
            }
            dfs(0,0);
            System.out.println( flag == true );
        }
    }
    public static void dfs(int start,double sum){
        //终止条件
        if(start==4){//搜索深度，四个数都所搜过了  0 1 2 3 
             if(sum == 24){
                 flag = true;
             }
        }else{
            start++;
            for(int i=0;i<4;i++){
                if(!visited[i]){
                    visited[i] = true;//标记访问过，避免重复访问
                    dfs(start,sum + nums[i]);
                    dfs(start,sum - nums[i]);
                    dfs(start,sum * nums[i]);
                    dfs(start,sum / nums[i]);//nums[i] 取1 - 10
                    visited[i] = false;//回溯
                }
            }
        }
    }
}