NobbZ

Advent of Code - Day 3

Note by the Moderators: This topic is to talk about Day 3 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.

And day 3 is solved as well.

On my VM in the office both parts take about 1 to 1.25 seconds. Thats OK for me today. But the first iteration I used to get the actual solutions has some repitions in it, which I do not like.

I really have to iterate on those, and perhaps I’ll be even able to get them more efficient?

gitlab.com/NobbZ/aoc_ex

lib/y2018/d3.ex

master

defmodule AocEx.Y2018.D3 do
  use AocEx.Boilerplate,
    transform: fn raw ->
      raw
      |> String.split("\n")
      |> Enum.map(&String.split/1)
      |> Enum.map(fn ["#" <> id, "@", coord, size] ->
        id = String.to_integer(id)

        coord =
          coord
          |> String.trim(":")
          |> String.split(",")
          |> Enum.map(&String.to_integer/1)
          |> List.to_tuple()

        size =
          size
          |> String.split("x")
          |> Enum.map(&String.to_integer/1)

This file has been truncated. show original

4 comments

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

1 1183 4

2018-12-04 08:38:29 UTC

First Post!

sorentwo

Oban Core Team

Finding a timely solution for Day 03 took me a little bit. Originally I wanted to use a range to detect overlap, but that wasn’t available so I moved on to constructing sets and counting from there. That wasn’t ideal either, and in the end using a simple map to count tuples was quick enough.

Post #1

Most Liked

yawaramin

I approached Day 3 as a set intersection problem, the only issue was finding a data structure to represent the claims that would be usable as set elements (i.e. comparable for uniqueness). I realized I could cleanly map each claim to a set of coordinates of the exact square inches of that claim; after that the solution fell into place as a series of set intersections and unions.

Here it is: advent_of_code_2018/lib/day3.ex at d65581aeb7b25f40d22a05c1435b1401b2505fef · yawaramin/advent_of_code_2018 · GitHub

Btw, I thought I’d share this fun fact that Elixir is in the top ten (at 10th) languages being used for Advent of Code projects on GitHub: Repository search results · GitHub

Post #3

Last Post!

debajit

My solution for Day 3 Part 1:

I’m reasonably happy with how it turned out.

(I spent quite a bit of time trying to learn how to use the Tensor library (Tensor.Matrix provides matrix operations). I also looked at Matrex, but failed to install it.

In the end I used a simple sparse matrix representation using a map with {row, col} => 1 items to represent the matrix. Using the regex named captures was fun — it was something I learned the hard way from a personal project previously.)

(Haven’t been able to look at Part 2 yet — its late night already, will look at it tomorrow)

github.com/debajit/advent-of-code-2018

day-03-part-1-slice.exs

master

defmodule Claim do
  defstruct [:id, :left, :top, :width, :height]

  @claim_regex ~r/^\#(?<id>\d+) @ (?<left>\d+),(?<top>\d+): (?<width>\d+)x(?<height>\d+)$/

  def from_string(claim_string) do
    %{"id" => id, "left" => left, "top" => top, "width" => width, "height" => height} =
      Regex.named_captures(@claim_regex, claim_string)

    %Claim{
      id: String.to_integer(id),
      left: String.to_integer(left),
      top: String.to_integer(top),
      width: String.to_integer(width),
      height: String.to_integer(height)
    }
  end
end

defmodule NoMatterHowYouSliceIt do

This file has been truncated. show original

Post #4

Where Next?

View thread on forum (has 4 replies!)

Switch to First Posts mode

coding-challenge

2018

advent-of-code

Home Learning Resources>Coding Challenges

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

2 1186 4

Last post

REPLY VIEW THREAD WITH 4 POSTS

Advent of Code - Day 3

NobbZ

Advent of Code - Day 3

First Post!

sorentwo

Most Liked

yawaramin

Last Post!

debajit

Where Next?

Popular in Challenges

Advent of Code 2020 - Day 10

Array merge in elixir

Advent of Code 2022 - Day 1

Advent of Code 2022 - Day 16

Advent of Code 2023 - Day 4

Advent of Code 2024 - Day 6

Advent of Code 2025 - Day 1

Other popular topics

Anonymous functions with multiple body

How To Implement if...else if...else condition

Upgrading Elixir - how to check versions, delete, and upgrade?

How to set environment variables in dev.exs?

Emacs - Elixir Setup Configuration Wiki

How can I write a raw sql query?

Learning Resources>Coding Challenges

Latest on Elixir Forum

Sponsor Spotlight

Our Sponsors

Categories:

Sub Categories:

Forums

Popular Tags

Our Sponsors

We're in Beta

Options