AdventOfCode/2023/day7.exs

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Elixir
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2023-12-07 13:23:29 +00:00
#!/usr/bin/env elixir
defmodule Day7 do
def part1(input) do
input
|> Enum.sort_by(&detect_type/1, &rank/2)
|> Enum.with_index()
|> Enum.map(fn {{_hand, bid}, rank} -> bid * (rank + 1) end)
|> Enum.sum()
end
def detect_type({hand, _bid}) do
frequencies =
hand
|> Enum.frequencies()
|> Enum.group_by(fn {_card, freq} -> freq end)
|> Map.new(fn {freq, cards} -> {freq, length(cards)} end)
type =
cond do
frequencies[5] -> :five_kind
frequencies[4] -> :four_kind
frequencies[3] && frequencies[2] -> :full_house
frequencies[3] -> :three_kind
frequencies[2] == 2 -> :two_pair
frequencies[2] -> :one_pair
true -> :high_card
end
{type, hand}
end
def rank({same_type, hand1}, {same_type, hand2}), do: tiebreak(hand1, hand2)
def rank({:high_card, _}, _), do: true
def rank({:one_pair, _}, {:high_card, _}), do: false
def rank({:one_pair, _}, _), do: true
def rank({:two_pair, _}, {b, _}) when b in [:high_card, :one_pair], do: false
def rank({:two_pair, _}, _), do: true
def rank({:three_kind, _}, {b, _}) when b in [:high_card, :one_pair, :two_pair], do: false
def rank({:three_kind, _}, _), do: true
def rank({:full_house, _}, {b, _}) when b in [:five_kind, :four_kind], do: true
def rank({:full_house, _}, _), do: false
def rank({:four_kind, _}, {:five_kind, _}), do: true
def rank({:four_kind, _}, _), do: false
def rank({:five_kind, _}, _), do: false
def tiebreak([first | resta], [first | restb]), do: tiebreak(resta, restb)
def tiebreak(["1" | _], _), do: true
def tiebreak(["2" | _], ["1" | _]), do: false
def tiebreak(["2" | _], _), do: true
def tiebreak(["3" | _], [b | _]) when b in ["1", "2"], do: false
def tiebreak(["3" | _], _), do: true
def tiebreak(["4" | _], [b | _]) when b in ["1", "2", "3"], do: false
def tiebreak(["4" | _], _), do: true
def tiebreak(["5" | _], [b | _]) when b in ["1", "2", "3", "4"], do: false
def tiebreak(["5" | _], _), do: true
def tiebreak(["6" | _], [b | _]) when b in ["1", "2", "3", "4", "5"], do: false
def tiebreak(["6" | _], _), do: true
def tiebreak(["7" | _], [b | _]) when b in ["1", "2", "3", "4", "5", "6"], do: false
def tiebreak(["7" | _], _), do: true
def tiebreak(["8" | _], [b | _]) when b in ["A", "K", "Q", "J", "T", "9"], do: true
def tiebreak(["8" | _], _), do: false
def tiebreak(["9" | _], [b | _]) when b in ["A", "K", "Q", "J", "T"], do: true
def tiebreak(["9" | _], _), do: false
def tiebreak(["T" | _], [b | _]) when b in ["A", "K", "Q", "J"], do: true
def tiebreak(["T" | _], _), do: false
def tiebreak(["J" | _], [b | _]) when b in ["A", "K", "Q"], do: true
def tiebreak(["J" | _], _), do: false
def tiebreak(["Q" | _], [b | _]) when b in ["A", "K"], do: true
def tiebreak(["Q" | _], _), do: false
def tiebreak(["K" | _], ["A" | _]), do: true
def tiebreak(["K" | _], _), do: false
def tiebreak(["A" | _], _), do: false
def part2(_input) do
:ok
end
def input do
with [input_filename] <- System.argv(),
{:ok, input} <- File.read(input_filename) do
input
|> String.split("\n", trim: true)
|> Enum.map(fn line ->
[hands, bid] = String.split(line)
{String.graphemes(hands), String.to_integer(bid)}
end)
else
_ -> :error
end
end
#######################
# HERE BE BOILERPLATE #
#######################
def run do
case input() do
:error -> print_usage()
input -> run_parts_with_timer(input)
end
end
defp run_parts_with_timer(input) do
run_with_timer(1, fn -> part1(input) end)
run_with_timer(2, fn -> part2(input) end)
end
defp run_with_timer(part, fun) do
{time, result} = :timer.tc(fun)
IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
IO.puts("#{inspect(result)}\n")
end
defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
defp format_time(μsec), do: "#{μsec / 1_000_000}s"
defp print_usage do
IO.puts("Usage: elixir day7.exs input_filename")
end
end
# Day7.run()