题解 | #24点运算#

const rl = require("readline").createInterface({ input: process.stdin });
var iter = rl[Symbol.asyncIterator]();
const readline = async () => (await iter.next()).value;

void (async function () {
    // Write your code here
    const queue = (arr, len) => {
        let res = []; // 所有排列结果
        let arrange = (tempArr, leftArr) => {
            // tempArr：排列好的元素 leftArr：待排列元素
            if (tempArr.length === len) {
                // 这里就是递归结束的地方
                res.push(tempArr.join("")); // 得到全排列的每个元素都是字符串
            } else {
                leftArr.forEach((item, index) => {
                    let temp = [].concat(leftArr);
                    temp.splice(index, 1);
                    // 第一个参数是当前分离出的元素所在数组；第二个参数temp是传入的leftArr去掉第一个后的结果
                    arrange(tempArr.concat(item), temp); // 这里使用了递归
                });
            }
        };
        arrange([], arr);
        return res;
    };

    const operations = [
        "+",
        "+",
        "+",
        "-",
        "-",
        "-",
        "*",
        "*",
        "*",
        "/",
        "/",
        "/",
    ];
    const operationQueue = queue(operations, 3);

    const trans = (a) => {
        switch (a) {
            case "A":
                return 1;
            case "J":
                return 11;
            case "Q":
                return 12;
            case "K":
                return 13;
            default:
                return parseInt(a);
        }
    };

    const calculate = (a, b, operation) => {
        switch (operation) {
            case "+":
                return trans(a) + trans(b);
            case "-":
                return trans(a) - trans(b);
            case "*":
                return trans(a) * trans(b);
            case "/":
                return parseInt(trans(a) / trans(b));
        }
    };

    while ((line = await readline())) {
        let tokens = line.split(" ");
        if (tokens.some((item) => item === "joker" || item === "JOKER")) {
            console.log("ERROR");
        } else {
            const cardsQueue = queue(tokens, 4);
            let isBreak = false;
            for (let cardsStr of cardsQueue) {
                for (let operationStr of operationQueue) {
                    let res1 = calculate(
                        cardsStr[0],
                        cardsStr[1],
                        operationStr[0]
                    );
                    let res2 = calculate(res1, cardsStr[2], operationStr[1]);
                    let res3 = calculate(res2, cardsStr[3], operationStr[2]);
                    if (res3 === 24) {
                        console.log(
                            cardsStr[0].concat(
                                operationStr[0],
                                cardsStr[1],
                                operationStr[1],
                                cardsStr[2],
                                operationStr[2],
                                cardsStr[3]
                            )
                        );
                        isBreak = true;
                        break;
                    }
                }
                if (isBreak) break;
            }
            if (!isBreak) console.log("NONE");
        }
    }
})();