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Day 10 complete
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‎2019/10/.formatter.exs

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# Used by "mix format"
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[
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inputs: ["{mix,.formatter}.exs", "{config,lib,test}/**/*.{ex,exs}"]
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]

‎2019/10/.gitignore

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# The directory Mix will write compiled artifacts to.
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/_build/
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# If you run "mix test --cover", coverage assets end up here.
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/cover/
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# The directory Mix downloads your dependencies sources to.
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/deps/
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# Where third-party dependencies like ExDoc output generated docs.
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/doc/
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# Ignore .fetch files in case you like to edit your project deps locally.
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/.fetch
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# If the VM crashes, it generates a dump, let's ignore it too.
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erl_crash.dump
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# Also ignore archive artifacts (built via "mix archive.build").
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*.ez
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# Ignore package tarball (built via "mix hex.build").
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aoc-*.tar
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‎2019/10/.projections.json

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{
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"lib/*.ex": {
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"type": "src",
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"alternate": "test/{}_test.exs",
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"template": [
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"# lib/{}.ex",
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"defmodule XXX do",
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"end"
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]
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},
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"test/*_test.exs": {
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"type": "test",
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"alternate": "lib/{}.ex",
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"template": [
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"# test/{}_test.exs",
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"defmodule XXX do",
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"end"
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]
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},
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}

‎2019/10/README.md

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# AOC
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**TODO: Add description**
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## Installation
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If [available in Hex](https://hex.pm/docs/publish), the package can be installed
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by adding `aoc` to your list of dependencies in `mix.exs`:
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```elixir
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def deps do
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[
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{:aoc, "~> 0.1.0"}
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]
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end
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```
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Documentation can be generated with [ExDoc](https://github.com/elixir-lang/ex_doc)
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and published on [HexDocs](https://hexdocs.pm). Once published, the docs can
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be found at [https://hexdocs.pm/aoc](https://hexdocs.pm/aoc).
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‎2019/10/config/config.exs

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# This file is responsible for configuring your application
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# and its dependencies with the aid of the Mix.Config module.
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use Mix.Config
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# This configuration is loaded before any dependency and is restricted
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# to this project. If another project depends on this project, this
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# file won't be loaded nor affect the parent project. For this reason,
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# if you want to provide default values for your application for
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# third-party users, it should be done in your "mix.exs" file.
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# You can configure your application as:
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#
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# config :aoc, key: :value
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#
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# and access this configuration in your application as:
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#
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# Application.get_env(:aoc, :key)
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#
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# You can also configure a third-party app:
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#
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# config :logger, level: :info
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#
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# It is also possible to import configuration files, relative to this
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# directory. For example, you can emulate configuration per environment
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# by uncommenting the line below and defining dev.exs, test.exs and such.
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# Configuration from the imported file will override the ones defined
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# here (which is why it is important to import them last).
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#
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# import_config "#{Mix.env()}.exs"

‎2019/10/input.txt

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.###.###.###.#####.#
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#####.##.###..###..#
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.#...####.###.######
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######.###.####.####
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#####..###..########
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#.##.###########.#.#
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##.###.######..#.#.#
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.#.##.###.#.####.###
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##..#.#.##.#########
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###.#######.###..##.
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###.###.##.##..####.
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.##.####.##########.
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#######.##.###.#####
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#####.##..####.#####
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##.#.#####.##.#.#..#
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###########.#######.
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#.##..#####.#####..#
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#####..#####.###.###
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####.#.############.
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####.#.#.##########.

‎2019/10/instructions.md

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--- Day 10: Monitoring Station ---
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----------------------------------
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You fly into the asteroid belt and reach the Ceres monitoring station.
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The Elves here have an emergency: they're having trouble tracking all of
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the asteroids and can't be sure they're safe.
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The Elves would like to build a new monitoring station in a nearby area
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of space; they hand you a map of all of the asteroids in that region
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(your puzzle input).
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The map indicates whether each position is empty (`.`) or contains an
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asteroid (`#`). The asteroids are much smaller than they appear on the
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map, and every asteroid is exactly in the center of its marked position.
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The asteroids can be described with `X,Y` coordinates where `X` is the
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distance from the left edge and `Y` is the distance from the top edge
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(so the top-left corner is `0,0` and the position immediately to its
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right is `1,0`).
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Your job is to figure out which asteroid would be the best place to
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build a *new monitoring station*. A monitoring station can *detect* any
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asteroid to which it has *direct line of sight* - that is, there cannot
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be another asteroid *exactly* between them. This line of sight can be at
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any angle, not just lines aligned to the grid or
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[diagonally]{title="The Elves on Ceres are clearly not concerned with honor."}.
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The *best* location is the asteroid that can *detect* the largest number
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of other asteroids.
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For example, consider the following map:
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.#..#
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.....
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#####
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....#
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...##
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The best location for a new monitoring station on this map is the
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highlighted asteroid at `3,4` because it can detect `8` asteroids, more
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than any other location. (The only asteroid it cannot detect is the one
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at `1,0`; its view of this asteroid is blocked by the asteroid at
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`2,2`.) All other asteroids are worse locations; they can detect `7` or
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fewer other asteroids. Here is the number of other asteroids a
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monitoring station on each asteroid could detect:
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.7..7
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.....
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67775
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....7
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...87
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Here is an asteroid (`#`) and some examples of the ways its line of
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sight might be blocked. If there were another asteroid at the location
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of a capital letter, the locations marked with the corresponding
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lowercase letter would be blocked and could not be detected:
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#.........
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...A......
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...B..a...
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.EDCG....a
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..F.c.b...
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.....c....
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..efd.c.gb
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.......c..
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....f...c.
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...e..d..c
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Here are some larger examples:
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- Best is `5,8` with `33` other asteroids detected:
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......#.#.
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#..#.#....
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..#######.
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.#.#.###..
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.#..#.....
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..#....#.#
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#..#....#.
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.##.#..###
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##...#..#.
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.#....####
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- Best is `1,2` with `35` other asteroids detected:
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#.#...#.#.
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.###....#.
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.#....#...
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##.#.#.#.#
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....#.#.#.
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.##..###.#
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..#...##..
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..##....##
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......#...
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.####.###.
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- Best is `6,3` with `41` other asteroids detected:
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.#..#..###
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####.###.#
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....###.#.
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..###.##.#
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##.##.#.#.
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....###..#
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..#.#..#.#
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#..#.#.###
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.##...##.#
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.....#.#..
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- Best is `11,13` with `210` other asteroids detected:
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.#..##.###...#######
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##.############..##.
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.#.######.########.#
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.###.#######.####.#.
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#####.##.#.##.###.##
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..#####..#.#########
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####################
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#.####....###.#.#.##
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##.#################
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#####.##.###..####..
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..######..##.#######
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####.##.####...##..#
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.#####..#.######.###
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##...#.##########...
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#.##########.#######
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.####.#.###.###.#.##
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....##.##.###..#####
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.#.#.###########.###
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#.#.#.#####.####.###
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###.##.####.##.#..##
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Find the best location for a new monitoring station. *How many other
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asteroids can be detected from that location?*
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Your puzzle answer was `214`.
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The first half of this puzzle is complete! It provides one gold star: \*
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--- Part Two --- {#part2}
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----------------
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Once you give them the coordinates, the Elves quickly deploy an Instant
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Monitoring Station to the location and discover [the
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worst]{title="The Elves on Ceres just have a unique system of values, that's all."}:
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there are simply too many asteroids.
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The only solution is *complete vaporization by giant laser*.
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Fortunately, in addition to an asteroid scanner, the new monitoring
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station also comes equipped with a giant rotating laser perfect for
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vaporizing asteroids. The laser starts by pointing *up* and always
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rotates *clockwise*, vaporizing any asteroid it hits.
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If multiple asteroids are *exactly* in line with the station, the laser
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only has enough power to vaporize *one* of them before continuing its
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rotation. In other words, the same asteroids that can be *detected* can
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be vaporized, but if vaporizing one asteroid makes another one
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detectable, the newly-detected asteroid won't be vaporized until the
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laser has returned to the same position by rotating a full 360 degrees.
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For example, consider the following map, where the asteroid with the new
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monitoring station (and laser) is marked `X`:
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.#....#####...#..
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##...##.#####..##
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##...#...#.#####.
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..#.....X...###..
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..#.#.....#....##
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The first nine asteroids to get vaporized, in order, would be:
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.#....###24...#..
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##...##.13#67..9#
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##...#...5.8####.
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..#.....X...###..
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..#.#.....#....##
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Note that some asteroids (the ones behind the asteroids marked `1`, `5`,
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and `7`) won't have a chance to be vaporized until the next full
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rotation. The laser continues rotating; the next nine to be vaporized
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are:
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.#....###.....#..
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##...##...#.....#
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##...#......1234.
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..#.....X...5##..
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..#.9.....8....76
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The next nine to be vaporized are then:
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.8....###.....#..
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56...9#...#.....#
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34...7...........
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..2.....X....##..
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..1..............
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Finally, the laser completes its first full rotation (`1` through `3`),
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a second rotation (`4` through `8`), and vaporizes the last asteroid
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(`9`) partway through its third rotation:
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......234.....6..
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......1...5.....7
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.................
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........X....89..
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.................
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In the large example above (the one with the best monitoring station
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location at `11,13`):
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- The 1st asteroid to be vaporized is at `11,12`.
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- The 2nd asteroid to be vaporized is at `12,1`.
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- The 3rd asteroid to be vaporized is at `12,2`.
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- The 10th asteroid to be vaporized is at `12,8`.
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- The 20th asteroid to be vaporized is at `16,0`.
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- The 50th asteroid to be vaporized is at `16,9`.
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- The 100th asteroid to be vaporized is at `10,16`.
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- The 199th asteroid to be vaporized is at `9,6`.
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- *The 200th asteroid to be vaporized is at `8,2`.*
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- The 201st asteroid to be vaporized is at `10,9`.
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- The 299th and final asteroid to be vaporized is at `11,1`.
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The Elves are placing bets on which will be the *200th* asteroid to be
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vaporized. Win the bet by determining which asteroid that will be; *what
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do you get if you multiply its X coordinate by `100` and then add its Y
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coordinate?* (For example, `8,2` becomes *`802`*.)
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Although it hasn't changed, you can still [get your puzzle
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input](10/input).
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Answer:
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You can also [\[Share[on
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[Twitter](https://twitter.com/intent/tweet?text=I%27ve+completed+Part+One+of+%22Monitoring+Station%22+%2D+Day+10+%2D+Advent+of+Code+2019&url=https%3A%2F%2Fadventofcode%2Ecom%2F2019%2Fday%2F10&related=ericwastl&hashtags=AdventOfCode)
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[Mastodon](javascript:void(0);)]{.share-content}\]]{.share} this puzzle.

‎2019/10/lib/aoc.ex

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defmodule AOC do
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def run do
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AOC.Runner.run
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end
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end

‎2019/10/lib/aoc/line_of_sight.ex

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defmodule AOC.LineOfSight do
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def polar(a, a), do: nil
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def polar({ox, oy}, {px, py}) do
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x = px - ox
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y = py - oy
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distance = :math.sqrt(:math.pow(x, 2) + :math.pow(y, 2))
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angle = :math.atan2(y, x)
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angle = angle * 180/:math.pi
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angle = if angle < 0, do: angle + 360 , else: angle
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angle = angle - 270
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angle = if angle < 0, do: angle + 360 , else: angle
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{ distance, angle, {px, py} }
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end
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end
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