day16.js

const fs = require('fs').promises;

(async () => {
  console.log(`Reading input from ${__dirname}/${process.argv[2]}.txt`);
  const inputData = await fs.readFile(`${__dirname}/${process.argv[2]}.txt`);
  const inputs = inputData
    .toString()
    .split('\n')
    .filter((n) => n);

  const rules = [];
  const yourTicket = [];
  const nearbyTickets = [];
  let foundTicket = false;
  let foundNearby = false;
  const rangeRegex = /(?<rangeName>.+): (?<lowerMin>\d+)-(?<lowerMax>\d+) or (?<upperMin>\d+)-(?<upperMax>\d+)/;

  for (let index = 0; index < inputs.length; index++) {
    const line = inputs[index];

    if (rangeRegex.test(line)) {
      const {
        rangeName,
        lowerMin,
        lowerMax,
        upperMin,
        upperMax,
      } = rangeRegex.exec(line).groups;
      rules.push({
        rangeName,
        lowerMax: parseInt(lowerMax, 10),
        lowerMin: parseInt(lowerMin, 10),
        upperMax: parseInt(upperMax, 10),
        upperMin: parseInt(upperMin, 10),
        index: [],
      });
      continue;
    }

    if (!foundTicket && line.includes('your ticket')) {
      foundTicket = true;
    }

    if (foundTicket && line.includes(',')) {
      foundTicket = false;
      line.split(',').forEach((l) => yourTicket.push(parseInt(l, 10)));
    }

    if (!foundNearby && line.includes('nearby tickets')) {
      foundNearby = true;
    }

    if (foundNearby && line.includes(',')) {
      nearbyTickets.push(line.split(',').map((l) => parseInt(l, 10)));
    }
  }

  let invalidRange = 0;
  const invalidTickets = new Set();
  nearbyTickets.forEach((nearByTicket, ticketIndex) => {
    for (let index = 0; index < nearByTicket.length; index++) {
      const num = nearByTicket[index];
      const valid = rules.some((rule) => {
        return (
          (num <= rule.lowerMax && num >= rule.lowerMin) ||
          (num <= rule.upperMax && num >= rule.upperMin)
        );
      });
      if (!valid) {
        invalidRange += num;
        invalidTickets.add(ticketIndex);
      }
    }
  });

  const validTickets = nearbyTickets.filter((_, i) => !invalidTickets.has(i));

  const allValues = [];
  yourTicket.forEach((value, index) => {
    const nums = [value, ...validTickets.map((t) => t[index])];
    nums.sort((a, b) => a - b);
    allValues.push(nums);
  });

  const updatedRules = rules.map((rule) => {
    for (let index = 0; index < allValues.length; index++) {
      const ticketNumbers = allValues[index];
      const allValid = ticketNumbers.every((num) => {
        return (
          (num <= rule.lowerMax && num >= rule.lowerMin) ||
          (num <= rule.upperMax && num >= rule.upperMin)
        );
      });

      if (allValid) {
        rule.index.push(index);
      }
    }
    return rule;
  });

  const savedRules = [];
  updatedRules
    .sort((a, b) => a.index.length - b.index.length)
    .map((r) => {
      r.index = r.index.filter((i) => !savedRules.includes(i));
      savedRules.push(r.index[0]);
    });

  const part2 = updatedRules
    .filter((rule) => rule.rangeName.startsWith('departure'))
    .reduce((sum, rule) => {
      return sum * yourTicket[rule.index[0]];
    }, 1);

  console.log('part1', invalidRange);
  console.log('---');
  console.log('part2', part2);
})();