题解 | #24点运算#先计算数字的全排列，再计算符号的全排列，再计算数字和符号能否组成24点

import java.util.*;

public class Main {
    public static HashMap<String,Integer> map = new HashMap<String,Integer>(){{
        put("A",1);
        put("2",2);
        put("3",3);
        put("4",4);
        put("5",5);
        put("6",6);
        put("7",7);
        put("8",8);
        put("9",9);
        put("10",10);
        put("J",11);
        put("Q",12);
        put("K",13);
    }};
    public static ArrayList<List<String>> res = new ArrayList<>();//数字的全排列
    public static ArrayList<String> path = new ArrayList<>();
    public static ArrayList<List<String>> resType = new ArrayList<>();//运算符号的全排列，4选3
    public static ArrayList<String> pathType = new ArrayList<>();
    public static String[] type = {"+","-","*","/"};//运算符号
    public static boolean flag = false;
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        // 注意 hasNext 和 hasNextLine 的区别
        while (in.hasNextLine()) { // 注意 while 处理多个 case
            flag = false;
            String[] game = in.nextLine().split("\\s");
            boolean[] visited = new boolean[game.length];
            if(containsJoker(game)){
                System.out.println("ERROR");
            }else{
                Arrays.sort(game);
                dfs(game,visited);
                dfsType(type);
                for(List<String> s1 : res){
                    for(List<String> s2 : resType){
                        if(cal(s1,s2) == 24){
                            StringBuilder sb = new StringBuilder();
                            for(int k=0;k<s1.size();k++){
                                sb.append(s1.get(k));
                                if(k<s2.size()){
                                    sb.append(s2.get(k));
                                }
                            }
                            flag = true;//有解
                            System.out.println(sb.toString());//输出一种情况即可
                            break;
                        }
                    }
                    if(flag){//有解直接退出
                        break;
                    }
                }
                if(!flag){//无解
                    System.out.println("NONE");
                }
            }
        }
    }
    public static boolean containsJoker(String[] game){
        for(String s : game){
            if(s.equals("JOKER") || s.equals("joker")){
                return true;
            }
        }
        return false;
    }
    //搜索所有数字的排列情况，剪枝去重
    public static void dfs(String[] game,boolean[] visited){
        //终止条件
        if(path.size()==game.length){
            res.add(new ArrayList<>(path));
            return;
        }
        for(int i=0;i<game.length;i++){
            if(i>0 && game[i] == game[i-1] && !visited[i-1]){
                continue;
            }
            if(!visited[i]){
                visited[i] = true;
                path.add(game[i]);
                dfs(game,visited);
                path.remove(path.size()-1);//回溯
                visited[i] = false;
            }
        }
    }
    //搜索所有运算符号的排列，4选3，允许重复
    public static void dfsType(String[] type){
        //终止条件
        if(pathType.size()==3){
            resType.add(new ArrayList<>(pathType));
            return;
        }
        for(int i=0;i<type.length;i++){
            pathType.add(type[i]);
            dfsType(type);
            pathType.remove(pathType.size()-1);//回溯
        }
    }
    //计算一个算式的结果，根据题意按从左到右计算即可
    public static int cal(List<String> listNum,List<String> listType){
        int res = map.get(listNum.get(0));//初始化为第一个数
        for(int i = 0;i<listType.size();i++){
            switch(listType.get(i)){
                case "+":
                    res += map.get(listNum.get(i+1));
                    break;
                case "-":
                    res -= map.get(listNum.get(i+1));
                    break;
                case "*":
                    res *= map.get(listNum.get(i+1));
                    break;
                case "/":
                    res /= map.get(listNum.get(i+1));
                    break;
            }
        }
        return res;
    }
}