Are you participating in the Advent of code this year?

If you don't know what the advent of code is, it's a website where you'll find a daily challenge (every day it gets harder). It's a really fun event, you should participate!

I try to solve the exercises using either JavaScript or TypeScript and will share my solutions daily (with one day delay so no one can cheat!). I only share the solution for the second part.

For day #7, I created a sort a tree like structure, but flat (I'm lazy), represented by a Record. Basically, for each color, you know which colors you can contains.

Once you have such a structure, finding the answer is just a matter of a small recursion:

const tree = input.reduce((tree, line) => {
  const color = /(^.*) bags contain/.exec(line)[1];
  tree[color] = [];

  const matches = line.matchAll(/,? (\d+) ([^,.]*) bags?/g);
  for (const match of matches) {
    for (let i = 0; i < parseInt(match[1]); i++) {
      tree[color].push(match[2]);
    }
  }
  return tree;
}, {});

const depth = (color) => {
  if (tree[color] === []) return 1;
  return tree[color].reduce((acc, color) => acc + depth(color), 1);
};

console.log(depth("shiny gold") - 1);

Feel free to share your solution in the comments!

Photo by Markus Spiske on Unsplash