AdventOfCode/2018/day3/day3.exs

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Elixir
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2021-12-26 13:10:19 +00:00
defmodule Coord do
defstruct [:x, :y]
end
defmodule Claim do
defstruct id: nil, pos: %Coord{x: 0, y: 0}, len: %Coord{x: 0, y: 0}
@input_pattern ~r/#(\d+) @ (\d+),(\d+): (\d+)x(\d+)/
def new_from_str(str) do
[id, pos_x, pos_y, len_x, len_y] =
Regex.run(@input_pattern, str, capture: :all_but_first)
|> Enum.map(&String.to_integer/1)
%Claim{id: id, pos: %Coord{x: pos_x, y: pos_y}, len: %Coord{x: len_x, y: len_y}}
end
def all_coords(claim) do
x_coords = claim.pos.x..(claim.pos.x + claim.len.x - 1)
y_coords = claim.pos.y..(claim.pos.y + claim.len.y - 1)
for x <- x_coords, y <- y_coords, do: %Coord{x: x, y: y}
end
def unshared?(claim, unshared_inches) do
Enum.all?(all_coords(claim), &MapSet.member?(unshared_inches, &1))
end
end
defmodule Day3 do
def count_claim_inches(claim, count) do
Enum.reduce(Claim.all_coords(claim), count, fn coord, count ->
Map.update(count, coord, 1, &(&1 + 1))
end)
end
def part1 do
File.stream!("input")
|> Stream.map(&Claim.new_from_str/1)
|> Enum.reduce(%{}, &count_claim_inches/2)
|> Stream.filter(fn {_coord, count} -> count >= 2 end)
|> Enum.count()
end
def part2 do
all_claims = File.stream!("input") |> Enum.map(&Claim.new_from_str/1)
unshared_inches =
all_claims
|> Enum.reduce(%{}, &count_claim_inches/2)
|> Enum.filter(fn {_coord, count} -> count == 1 end)
|> MapSet.new(fn {coord, _count} -> coord end)
Enum.find(all_claims, &Claim.unshared?(&1, unshared_inches))
end
end
IO.puts("Part1 (number of square inches claimed multiple times): #{Day3.part1()}")
IO.puts("Part2 (id of only claim not overlapping with another): #{Day3.part2().id}")