leetcode-go/oj/360-2019-spring/24point.js

function solve24point(...numbers) {
    class Operation {
        constructor(val, rank, exp) {
            this.val = val;
            this.rank = rank;
            this.exp = exp;
        }

        plus(that) {
            return new Operation(this.val + that.val, 0, `${this.exp}+${that.exp}`);
        }

        minus(that) {
            let exp;
            if (that.rank === 0) exp = `${this.exp}-(${that.exp})`;
            else exp = `${this.exp}-${that.exp}`;
            return new Operation(this.val - that.val, 0, exp);
        }

        mult(that) {
            let exp;
            if (this.rank === 0 && that.rank === 0) exp = `(${this.exp})*(${that.exp})`;
            else if (this.rank === 0) exp = `(${this.exp})*${that.exp}`;
            else if (that.rank === 0) exp = `${this.exp}*(${that.exp})`;
            else exp = `${this.exp}*${that.exp}`;
            return new Operation(this.val * that.val, 1, exp);
        }

        div(that) {
            let exp;
            if (this.rank === 0 && that.rank !== 2) exp = `(${this.exp})/(${that.exp})`;
            else if (this.rank === 0) exp = `(${this.exp})/${that.exp}`;
            else if (that.rank !== 2) exp = `${this.exp}/(${that.exp})`;
            else exp = `${this.exp}/${that.exp}`;
            return new Operation(this.val / that.val, 1, exp);
        }
    }

    const eps = 0.000001;

    function dfs(nums) {
        if (nums.length === 1 && Math.abs(nums[0].val - 24.0) < eps) return nums[0].exp;
        for (let i = 0; i < nums.length - 1; i++) {
            for (let j = i + 1; j < nums.length; j++) {
                let next = new Array(nums.length - 2);
                for (let k = 0, idx = 0; k < nums.length; k++) {
                    if (k == i || k == j) continue;
                    next[idx++] = nums[k];
                }
                let p = nums[i], q = nums[j];
                let tmp = [p.plus(q), p.minus(q), q.minus(p), p.mult(q)];
                if (q.val > 0) tmp.push(p.div(q));
                if (p.val > 0) tmp.push(q.div(p));
                for (let i = 0; i < tmp.length; i++) {
                    next.push(tmp[i]);
                    const res = dfs(next);
                    if (res !== null) return res;
                    next.pop();
                }
            }
        }
        return null;
    }

    const nums = new Array(numbers.length);
    for (let i = 0; i < numbers.length; i++) {
        nums[i] = new Operation(numbers[i], 2, numbers[i]);
    }
    return dfs(nums);
}


// eslint-disable-next-line no-console
const log = console.log.bind(console);

log(solve24point(2, 4, 1, 8));
log(solve24point(2, 4, 6, 8));
log(solve24point(1, 2, 5, 8));
log(solve24point(1, 7, 8, 8));
log(solve24point(6, 6, 6, 6, 6));
log(solve24point(1, 5, 5, 5));
log(solve24point(2, 5, 5, 10));
log(solve24point(1, 4, 5, 6));
log(solve24point(6, 9, 9, 10));