advent-of-code-2017-d04p2-boring.js

// Usage: node advent-of-code-2017-d04p2-boring.js /path/to/input.txt

// This boring version works by lexicographically sorting the characters
// in each word of the pass phrase, and then adding them all to a set.
// If the size of the set is less than the number of words in the
// passphrase, then at least one pair of words were anagrams of each
// other and the passphrase invalid.

'use strict';

const input = require('fs').readFileSync(process.argv[2], 'utf8').trim();

function sortCharactersInWord(word) {
  // Default sort is, for once, exactly what we need!
  return Array.from(word).sort().join('');
}

let valid = 0;

for (const line of input.split('\n')) {
  const wordsList = line.trim().split(/\s+/);
  const sortedCharactersWordsList = wordsList.map(sortCharactersInWord);
  const sortedCharactersWordsSet = new Set(sortedCharactersWordsList);

  // Sets contain only unique values, which I exploit here to find duplicates.
  if (sortedCharactersWordsSet.size === sortedCharactersWordsList.length) {
    valid++;
  }
}

console.log(valid);

advent-of-code-2017-d04p2.js

// Usage: node advent-of-code-2017-d04p2.js /path/to/input.txt
// Take care, works for shortish words only (fine for this problem),
// at least until arbitrary sized integers make it into JS.

'use strict';

const input = require('fs').readFileSync(process.argv[2], 'utf8').trim();

// Assign a prime to each letter. The product of primes for a word will
// equal another word only if they are anagrams of each other.
const letterPrimes = {
  a:  2, b:  3, c:  5, d:  7, e: 11, f: 13, g: 17,
  h: 19, i: 23, j: 29, k: 31, l: 37, m: 41, n: 43,
  o: 47, p: 53, q: 59, r: 61, s: 67, t: 71, u: 73,
  v: 79, w: 83, x: 89, y: 97, z: 101
};

function calculateWordValue(word) {
  return [...word].reduce((total, letter) => total *= letterPrimes[letter], 1);
}

let valid = 0;

for (const line of input.split('\n')) {
  const wordsList = line.trim().split(/\s+/);
  const valuesList = wordsList.map(word => calculateWordValue(word));
  const valuesSet = new Set(valuesList);

  // Sets contain only unique values, which I exploit here to find duplicates.
  if (valuesSet.size === valuesList.length) {
    valid++;
  }
}

console.log(valid);

Two solutions. One boring one based upon sorting the characters in each word of a passphrase, and one more intersting (but which breaks for larger words than encountered in the input) based on products of primes.