AdventOfCode/day12/day12part2.exs

28 lines
1.2 KiB
Elixir

defmodule Day12Part2 do
def run do
File.read!("input")
|> String.split("\n", trim: true)
|> Enum.map(fn <<action::binary-1>> <> value -> {action, String.to_integer(value)} end)
|> Enum.reduce({{0, 0}, {10, 1}}, &process/2)
|> manhattan_distance()
|> IO.puts()
end
def process({"N", value}, {boat, {vx, vy}}), do: {boat, {vx, vy + value}}
def process({"S", value}, {boat, {vx, vy}}), do: {boat, {vx, vy - value}}
def process({"E", value}, {boat, {vx, vy}}), do: {boat, {vx + value, vy}}
def process({"W", value}, {boat, {vx, vy}}), do: {boat, {vx - value, vy}}
def process({"L", value}, {boat, waypoint}), do: {boat, rotate_left(waypoint, value)}
def process({"R", value}, {boat, waypoint}), do: {boat, rotate_right(waypoint, value)}
def process({"F", value}, {{x, y}, {vx, vy}}), do: {{x + vx * value, y + vy * value}, {vx, vy}}
def rotate_left(waypoint, 0), do: waypoint
def rotate_left({vx, vy}, degrees), do: rotate_left({-vy, vx}, degrees - 90)
def rotate_right(waypoint, 0), do: waypoint
def rotate_right({vx, vy}, degrees), do: rotate_right({vy, -vx}, degrees - 90)
def manhattan_distance({{x, y}, _}), do: abs(x) + abs(y)
end
Day12Part2.run()