sneako

Advent of Code - Day 1

Note by the Moderators: This topic is to talk about the first day of the Advent of Code.

For general discussion about the Advent of Code 2018 and links to topics of the other days, see this topic.

Nice one, mine came out quite similar: solution & test

10 comments

#coding-challenge #2018 #advent-of-code

24 2017 10

2023-11-28 06:08:30 UTC

Most Liked

simon

I’m doing this too and my solution is very similar to other ones already posted.

I’m fairly new to Elixir and only using it as and when I can for a side-project so I learnt a few new things…

Stream.cycle() was new to me and I had to Google to find it.
Enum.reduce_while was also a new discovery but at least I found this one by looking through the documentation.
List is really slow and MapSet is really fast when checking for existing items. My first solution used List and was fine for the tests I built but I thought that I had a bug and an infinite loop when I ran the full set of data for the challenge. Once it eventually finished I thought that there must be a faster way and looked at the documentation.

Overall it was a fun little challenge and exactly what I hoped it would be… something to get me to learn new things, not just a test to see if I know it all.

I’m really looking forward to watching José’s Twitch streams about these challenges too.

Post #3

yawaramin

Just finished Day 1 both parts, the fun thing with Advent of Code is that basically anything that deals with reading an input file and doing some calculation on it is a prime candidate for File.stream and then Stream processing–we have it really easy in the Elixir world.

Post #8

arhyth

I’ve been working in elixir for a year now and most of the language “constructs” I used in this day’'s solutions including the ones you mentioned were all new to me. My implementation for the second problem used lists and was very slow. I tried it with mapsets after looking at others solutions and wow what a difference.

After this first day, I’m also looking forward to the next days and to Jose’s twitch streams.

Post #10

connorlay

Ah nice! Great minds I guess

Post #2

factoryd

I decided to partake as well. Surprise surprise. I ended up with a very similar solution.

github.com

trbngr/advent_of_code_2018/blob/master/lib/day_1/chronal_calibration.ex

defmodule Day1.ChronalCalibration do
  def part_one, do: Enum.sum(read_input())

  def part_two(state \\ {0, MapSet.new()}) do
    read_input()
    |> Enum.reduce_while(state, &update_frequency/2)
    |> halt_on_duplicate_frequency
  end

  defp halt_on_duplicate_frequency(n) when is_integer(n), do: n
  defp halt_on_duplicate_frequency(state), do: part_two(state)

  defp update_frequency(n, {frequency, history}) do
    new_frequency = frequency + n

    case MapSet.member?(history, new_frequency) do
      true -> {:halt, new_frequency}
      false -> {:cont, {new_frequency, MapSet.put(history, new_frequency)}}
    end
  end

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Post #5

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#coding-challenge #2018 #advent-of-code

24 2018 10

Last post

Advent of Code - Day 1

sneako

Advent of Code - Day 1

Most Liked

simon

yawaramin

arhyth

connorlay

factoryd

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