134 lines
3.5 KiB
Elixir
134 lines
3.5 KiB
Elixir
defmodule Day4 do
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@rows for y <- 0..4, do: for(x <- 0..4, do: {x, y})
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@cols for x <- 0..4, do: for(y <- 0..4, do: {x, y})
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def part1(input) do
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{current_number, winning_board} = play(input)
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sum_unmarked(winning_board) * current_number
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end
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def part2(input) do
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{current_number, last_board} = play_until_last(input)
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sum_unmarked(last_board) * current_number
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end
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def play({[current_number | next_numbers], boards}) do
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boards = for board <- boards, do: mark(board, current_number)
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case check_for_winner(boards) do
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nil -> play({next_numbers, boards})
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board -> {current_number, board}
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end
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end
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def play_until_last({_numbers, [_last_board]} = input), do: play(input)
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def play_until_last({numbers, boards} = input) do
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{_current_number, current_winner} = play(input)
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current_winner_no_markers = Map.new(current_winner, fn {k, {v, _marker}} -> {k, v} end)
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remaining_boards =
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Enum.reject(boards, fn board ->
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current_winner_no_markers == Map.new(board, fn {k, {v, _marker}} -> {k, v} end)
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end)
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play_until_last({numbers, remaining_boards})
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end
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def sum_unmarked(board) do
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board
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|> Enum.filter(&match?({_key, {_number, false}}, &1))
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|> Enum.map(fn {_key, {number, _marked}} -> number end)
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|> Enum.sum()
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end
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def mark(board, current_number) do
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case Enum.find(board, &match?({_key, {^current_number, false}}, &1)) do
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nil -> board
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{key, _value} -> Map.put(board, key, {current_number, true})
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end
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end
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def check_for_winner([]), do: nil
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def check_for_winner([board | boards]) do
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row_complete? =
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Enum.any?(@rows, fn row ->
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values = for key <- row, do: board[key]
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Enum.all?(values, &match?({_number, true}, &1))
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end)
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col_complete? =
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Enum.any?(@cols, fn col ->
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values = for key <- col, do: board[key]
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Enum.all?(values, &match?({_number, true}, &1))
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end)
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if row_complete? or col_complete? do
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board
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else
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check_for_winner(boards)
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end
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end
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def input do
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with [input_filename] <- System.argv(),
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{:ok, input} <- File.read(input_filename) do
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[numbers | boards] = String.split(input, "\n", trim: true)
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numbers = numbers |> String.split(",") |> Enum.map(&String.to_integer/1)
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boards = parse_boards(boards)
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{numbers, boards}
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else
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_ -> :error
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end
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end
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defp parse_boards([]), do: []
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defp parse_boards(boards) do
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{board, boards} = Enum.split(boards, 5)
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board = Enum.map(board, &String.split/1)
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board =
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for {row, y} <- Enum.with_index(board), {value, x} <- Enum.with_index(row), into: %{} do
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{{x, y}, {String.to_integer(value), false}}
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end
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[board | parse_boards(boards)]
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end
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#######################
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# HERE BE BOILERPLATE #
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#######################
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def run do
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case input() do
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:error -> print_usage()
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input -> run_parts_with_timer(input)
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end
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end
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defp run_parts_with_timer(input) do
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run_with_timer(1, fn -> part1(input) end)
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run_with_timer(2, fn -> part2(input) end)
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end
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defp run_with_timer(part, fun) do
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{time, result} = :timer.tc(fun)
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IO.puts("Part #{part} (completed in #{format_time(time)}):\n")
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IO.puts("#{result}\n")
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end
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defp format_time(μsec) when μsec < 1_000, do: "#{μsec}μs"
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defp format_time(μsec) when μsec < 1_000_000, do: "#{μsec / 1000}ms"
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defp format_time(μsec), do: "#{μsec / 1_000_000}s"
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defp print_usage do
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IO.puts("Usage: elixir day4.exs input_filename")
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end
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end
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Day4.run()
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