adventofcode/2021/10/part2.mjs

import fs from "fs-extra";
import fp from "lodash/fp.js";
import _ from "lodash";

import * as p1 from "./part1.mjs";

function completionString(line) {
    const stack = [];

    for (const c of line) {
        if (p1.closing[c]) {
            stack.unshift(p1.closing[c]);
        } else if (c !== stack.shift()) {
            return;
        }
    }

    return stack;
}

export function linesScore(lines) {
    lines = lines.map(completionString).filter((x) => x);

    const points = {
        ")": 1,
        "]": 2,
        "}": 3,
        ">": 4,
    };

    const lineScore = (line) => line.reduce((a, b) => 5 * a + points[b], 0);

    return lines.map(lineScore);
}

export function solution(lines) {
    const scores = linesScore(lines);

    scores.sort((a, b) => (a < b ? -1 : 1));

    return scores[(scores.length - 1) / 2];
}