day10.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)
    .map((n) => parseInt(n, 10))
    .sort((a, b) => a - b);

  const max = inputs[inputs.length - 1] + 3;

  inputs.unshift(0);
  inputs.push(max);

  const inputSet = new Set(inputs);
  let jolts = 0;
  let oneUps = 0;
  let twoUps = 0;
  let threeUps = 0;
  for (let index = 0; index < inputs.length + 1; index++) {
    for (let j = 1; j < 4; j++) {
      if (inputSet.has(jolts + j)) {
        jolts += j;
        if (j === 1) oneUps++;
        if (j === 2) twoUps++;
        if (j === 3) threeUps++;
        break;
      }
    }
  }

  console.log('partOne', oneUps * threeUps);

  console.log('----');

  const cache = new Map();
  const permutations = (val) => {
    if (cache.has(val)) {
      return cache.get(val);
    }

    const callBack = (lastValue) => {
      if (lastValue === max) {
        return 1;
      }

      let count = 0;
      for (let index = 1; index < 4; index++) {
        if (inputSet.has(lastValue + index)) {
          count += permutations(lastValue + index);
        }
      }

      return count;
    };

    const output = callBack(val);

    cache.set(val, output);

    return output;
  };

  console.log('part2', permutations(0));
})();