64 lines
1.3 KiB
Elixir
64 lines
1.3 KiB
Elixir
defmodule Day3 do
|
|
@example """
|
|
..##.......
|
|
#...#...#..
|
|
.#....#..#.
|
|
..#.#...#.#
|
|
.#...##..#.
|
|
..#.##.....
|
|
.#.#.#....#
|
|
.#........#
|
|
#.##...#...
|
|
#...##....#
|
|
.#..#...#.#
|
|
"""
|
|
|
|
def part1(example \\ false) do
|
|
count_trees(example, {3, 1})
|
|
end
|
|
|
|
def part2(example \\ false) do
|
|
one_one = count_trees(example, {1, 1})
|
|
three_one = count_trees(example, {3, 1})
|
|
five_one = count_trees(example, {5, 1})
|
|
seven_one = count_trees(example, {7, 1})
|
|
one_two = count_trees(example, {1, 2})
|
|
|
|
one_one * three_one * five_one * seven_one * one_two
|
|
end
|
|
|
|
def count_trees(example, slope) do
|
|
example
|
|
|> parse_input()
|
|
|> count_trees_for_slope(slope)
|
|
end
|
|
|
|
def parse_input(example) do
|
|
if(example, do: @example, else: File.read!("lib/day3/input.txt"))
|
|
|> String.trim()
|
|
|> String.split("\n")
|
|
|> Enum.map(fn line ->
|
|
line
|
|
|> String.codepoints()
|
|
|> Enum.map(fn
|
|
"#" -> 1
|
|
_ -> 0
|
|
end)
|
|
|> Stream.cycle()
|
|
end)
|
|
end
|
|
|
|
def count_trees_for_slope(lines, slope) do
|
|
do_count(lines, slope, 0, 0)
|
|
end
|
|
|
|
def do_count([current | rest], {dx, dy} = slope, x, trees) do
|
|
rest = Enum.drop(rest, dy - 1)
|
|
do_count(rest, slope, x + dx, trees + Enum.at(current, x))
|
|
end
|
|
|
|
def do_count([], _, _, trees) do
|
|
trees
|
|
end
|
|
end
|