Advent of Code

day2.js

/* ----------------------- PART 1 ----------------------- */
const countLetters = (string) => {
  const seen = {};
  const letters = string.split('');
  _.forEach(letters, (char) => {
    if (!seen[char]) {
      seen[char] = 1;
    } else {
      seen[char]++;
    }
  })
  return seen;
};

const checkSum = (arr) => {
  const twoCount = 0;
  const threeCount = 0;

  let objects = _.map(arr, countLetters);
  _.forEach(objects, obj => {
    if (_.some(obj, letterCount => letterCount === 2)) {
      twoCount++;
    }

    if (_.some(obj, letterCount => letterCount === 3)) {
      threeCount++;
    }
  });

  return twoCount * threeCount;
};

checkSum(arr); // 7105


/* ----------------------- PART 2 ----------------------- */


const removeChars = (arr) => {
  let arrOfChars = arr[0].split('');
  let answer = null;
  for (let i = 0; i < arrOfChars.length; i++) {
    let seen = {};
    _.each(arr, (string) => {
      let modifiedString = string.slice(0, i) + string.slice(i + 1);
      if (!seen[modifiedString]) {
        seen[modifiedString] = true;
      } else {
        answer = modifiedString;
        return false;
      }
    });
    if (answer) break;
  }

  return answer;
};

removeChars(arr); // 'omlvgdokxfncvqyersasjziup'