Advent of Code 2015 - Day 8 - Matchsticks

On the eighth day of Advent of Code 2015 Santa wants to know how much space his newly digitised list will take up when stored.

Part 1

Based on the supplied input list of string literals; part one asks us to tally up the additional space this literal interpretation takes us as opposed to their in-memory representations. When parsing each string literal we need to take into consideration any escape sequences and hexadecimal notation. This problem feels like it could be solved using Regular Expression patterns, however, upon examination we may be able to harness a couple of in-built JavaScript functions to do alot of the heavy lifting.

const part1 = (input: string): number =>
  input
    .split('\n')
    .reduce(
      (total, line) => total + (line.length - eval(line).length),
      0
    );

Using the dreaded eval function we are able to leverage JavaScript in evaluating each provided string literal, returning to us the in-memory represenation. Although I would refrain from using this approach with untrusted input, in a small puzzle like this it provides a very succinct solution. Reducing over the input listing tallying up the length differences along the way, we are able to produce the desired answer 🌟.

Part 2

In part two we are asked to apply an additional encoding on the provided string literals, returning the total difference between the encoded and original input.

const part2 = (input: string): number =>
  input
    .split('\n')
    .reduce(
      (total, line) =>
        total + (JSON.stringify(line).length - line.length),
      0
    );

Again, we are able to harness another built-in function JSON.stringify which will provide us with the desired escape sequences and quotes. Reducing over the input listing we can tally up these length differences and return the answer we require 🌟.

To summarise, todays solutions depend greatly on functionality provided by the chosen language (JavaScript). In the future I hope to spend a little more time exploring how we could leverage Regular Expressions to solve this problem in a more translatable mannor.