advent-code-2021-day-10.js

let raw = `[({(<(())[]>[[{[]{<()<>>
  [(()[<>])]({[<{<<[]>>(
  {([(<{}[<>[]}>{[]{[(<()>
  (((({<>}<{<{<>}{[]{[]{}
  [[<[([]))<([[{}[[()]]]
  [{[{({}]{}}([{[{{{}}([]
  {<[[]]>}<{[{[{[]{()[[[]
  [<(<(<(<{}))><([]([]()
  <{([([[(<>()){}]>(<<{{
  <{([{{}}[<[[[<>{}]]]>[]]`;

let brackets = [
  ["(", ")"],
  ["{", "}"],
  ["[", "]"],
  ["<", ">"],
];

function isLeft(char) {
  return brackets.some((b) => b[0] === char);
}

function getLeft(char) {
  return brackets.find((b) => b[1] === char)[0];
}

function getRight(char) {
  return brackets.find((b) => b[0] === char)[1];
}

function fix(chars = []) {
  let stack = [];
  for (let i = 0; i < chars.length; i++) {
    let char = chars[i];
    if (isLeft(char)) {
      stack.push(char);
    } else {
      if (stack.length === 0 || stack.pop() !== getLeft(char)) {
        return;
      }
    }
  }
  return stack.reverse().map((c) => getRight(c));
}

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

function run(input = "") {
  let lines = input
    .split("\n")
    .filter(Boolean)
    .map((l) => l.trim().split(""));
  let res = lines.map((line) => fix(line)).filter(Boolean);
  let scores = res.map((chars) => chars.reduce((a, b) => a * 5 + points[b], 0));
  scores.sort((a, b) => b - a);
  console.log(res, scores, scores[(scores.length - 1) / 2]);
}

run(raw);