AoC 2024 Day 19

aoc-2024-day-19.js

import { filter, length, sum } from "@/lib/arrays";
import { memo, pipe } from "@/lib/utils.js";

const parse = input =>
  (([g1, g2]) => [
    g1.split(",").map(v => v.trim()),
    g2.split("\n"),
  ])(input.split("\n\n"));

export const part1 = pipe(
  parse,
  ([patterns, designs]) => {
    const isPossible = memo(
      d =>
        d === "" ||
        patterns
          .filter(p => d.startsWith(p))
          .map(p => d.substring(p.length))
          .filter(rest => isPossible(rest)).length > 0
    );
    return designs.map(d => isPossible(d));
  },
  filter(Boolean),
  length
);

export const part2 = pipe(
  parse,
  ([patterns, designs]) => {
    const combinations = memo(d =>
      d === ""
        ? 1
        : patterns
            .filter(p => d.startsWith(p))
            .map(p => d.substring(p.length))
            .reduce(
              (sum, rest) => sum + combinations(rest),
              0
            )
    );
    return designs.map(d => combinations(d));
  },
  sum
);