Last active
December 7, 2018 16:07
-
-
Save egze/217b741254be537543d60ed84423e75c to your computer and use it in GitHub Desktop.
AoC Day5 solution
This file contains bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
| defmodule Polymer do | |
| defstruct data: [] | |
| def new do | |
| %Polymer{} | |
| end | |
| def size(%Polymer{data: data}) do | |
| data |> Enum.count() | |
| end | |
| defimpl Collectable do | |
| def into(%Polymer{data: data}) do | |
| collector_fun = fn | |
| [] = data, {:cont, elem} -> | |
| [elem | data] | |
| [last | rest] = data, {:cont, elem} -> | |
| cond do | |
| elem == last -> [elem | data] | |
| elem != last && String.capitalize(elem) == String.capitalize(last) -> rest | |
| true -> [elem | data] | |
| end | |
| data, :done -> | |
| %Polymer{data: data} | |
| _, :halt -> | |
| :ok | |
| end | |
| {data, collector_fun} | |
| end | |
| end | |
| end | |
| defmodule Day5 do | |
| def part1 do | |
| [line | _rest] = File.read!("input.txt") |> String.split("\n", trim: true) | |
| line | |
| |> String.split("", trim: true) | |
| |> compute_polymer | |
| end | |
| def part2 do | |
| [line | _rest] = File.read!("input.txt") |> String.split("\n", trim: true) | |
| polymer = | |
| line | |
| |> String.split("", trim: true) | |
| |> generate_clean_lists | |
| |> Enum.min_by(fn polymer -> | |
| Polymer.size(polymer) | |
| end) | |
| Polymer.size(polymer) | |
| end | |
| @doc """ | |
| Computes the final polymer size | |
| iex> Day5.compute_polymer(["a", "b", "B", "c", "D", "d", "a"]) | |
| 3 | |
| """ | |
| def compute_polymer(chars) do | |
| polymer = for char <- chars, do: char, into: Polymer.new() | |
| Polymer.size(polymer) | |
| end | |
| def generate_clean_lists(chars) do | |
| Enum.map(?a..?z, fn x -> <<x::utf8>> end) | |
| |> Enum.map(fn char -> | |
| clean_chars = | |
| Enum.reject(chars, fn x -> | |
| String.capitalize(x) == String.capitalize(char) | |
| end) | |
| for char <- clean_chars, do: char, into: Polymer.new() | |
| end) | |
| end | |
| end |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment