day05.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 seats = [];

  inputs.forEach((seat) => {
    const range = {
      minRow: 0,
      maxRow: 127,
      minCol: 0,
      maxCol: 7,
      id: 1,
    };
    const steps = seat.split('');
    // F, L means to take the lower half
    // B, R means to take the upper half,
    steps.forEach((l) => {
      if (l === 'F') {
        range.maxRow = Math.floor(
          range.maxRow - (range.maxRow - range.minRow + 1) / 2
        );
      } else if (l === 'B') {
        range.minRow = Math.floor(
          range.minRow + (range.maxRow - range.minRow + 1) / 2
        );
      } else if (l === 'R') {
        range.minCol = Math.floor(
          range.minCol + (range.maxCol - range.minCol + 1) / 2
        );
      } else {
        range.maxCol = Math.floor(
          range.maxCol - (range.maxCol - range.minCol + 1) / 2
        );
      }
    });

    range.id = 8 * range.minRow + range.maxCol;

    // Parse row/col with binary
    // parseInt(seat.substr(0, 7).replaceAll('F', '0').replaceAll('B', '1'), 2);
    // parseInt(seat.substr(7, 10).replaceAll('R', '1').replaceAll('L', '0'), 2);

    seats.push(range);
  });

  console.log(
    'max seat id',
    seats.reduce((max, { id }) => {
      return max < id ? id : max;
    }, -Infinity)
  );

  let lastId = 99;

  seats
    .map(({ id }) => id)
    .sort((a, b) => a - b)
    .forEach((id) => {
      if (id - lastId === 2) {
        console.log('your seat', lastId + 1);
      }
      lastId = id;
    });
})();