Day 5: Cafeteria
Mix.install([{:kino, "~> 0.11.3"}])
Day 5
sample_input = Kino.Input.textarea("Paste Sample Input")
real_input = Kino.Input.textarea("Paste Real Input")
defmodule Cafeteria do
def part1(input) do
{ranges, ids} = parse(input)
Enum.count(ids, fn id -> Enum.find(ranges, & in_range?(id, &1)) end)
end
def part2(input) do
{ranges, _ids} = parse(input)
ranges
|> Enum.reduce([], fn range, consolidated ->
incorporate_range(range, consolidated)
end)
|> Enum.sum_by(fn {lower, upper} -> upper - lower + 1 end)
end
defp parse(input) do
[raw_ranges, raw_ids] =
input
|> Kino.Input.read()
|> String.split("\n\n")
ranges =
raw_ranges
|> String.split("\n", trim: true)
|> Enum.map(fn range ->
range |> String.split("-") |> Enum.map(&String.to_integer/1) |> List.to_tuple()
end)
ids = raw_ids |> String.split("\n", trim: true) |> Enum.map(&String.to_integer/1)
{ranges, ids}
end
defp in_range?(id, {lower, upper}) when id >= lower and id <= upper, do: true
defp in_range?(_, _), do: false
defp incorporate_range(range, remaining, visited \\ [])
# no ranges left, add our new range at the end
defp incorporate_range(range, [], visited), do: visited ++ [range]
# new range is strictly less than the next range in the list
defp incorporate_range({lower, upper}, [{e_lower, _} | _] = remaining, visited) when upper < e_lower do
visited ++ [{lower, upper}] ++ remaining
end
# new range is strictly greater than the next range in the list
# add that one to the visited list and continue
defp incorporate_range({lower, upper}, [{e_lower, e_upper} | rest], visited) when lower > e_upper do
incorporate_range({lower, upper}, rest, visited ++ [{e_lower, e_upper}])
end
# new range must overlap with the next range in the list
# merge them together and then incorporate that combined range
defp incorporate_range({lower, upper}, [{e_lower, e_upper} | rest], visited) do
incorporate_range({min(lower, e_lower), max(upper, e_upper)}, rest, visited)
end
end
Cafeteria.part1(sample_input)
Cafeteria.part1(real_input)
Cafeteria.part2(sample_input)
Cafeteria.part2(real_input)
