95 lines
1.9 KiB
Rust
95 lines
1.9 KiB
Rust
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#![feature(test)]
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extern crate test;
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use itertools::Itertools;
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#[derive(Debug, PartialEq)]
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enum Tile {
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Free,
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Tree,
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}
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type Forest = Vec<Vec<Tile>>;
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const STEP_RIGHT: [usize; 5] = [1, 3, 5, 7, 1];
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const STEP_DOWN: [usize; 5] = [1, 1, 1, 1, 2];
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impl From<char> for Tile {
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fn from(c: char) -> Self {
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match c {
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'.' => Tile::Free,
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'#' => Tile::Tree,
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_ => unreachable!(),
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}
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}
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}
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fn read_input() -> String {
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std::fs::read_to_string("input").unwrap()
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}
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fn parse_input(raw: &str) -> Forest {
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raw.lines().map(|l| l.chars().map_into().collect()).collect()
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}
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fn count_all_paths(forest: &Forest) -> usize {
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STEP_RIGHT.iter().zip(STEP_DOWN.iter())
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.map(|(&r, &d)| count_trees(forest, r, d))
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.product()
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}
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fn count_trees(forest: &Forest, step_right: usize, step_down: usize) -> usize {
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let mut x = 0;
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let mut y = 0;
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let mut trees = 0;
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let width = forest[0].len();
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while y < forest.len() {
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trees += (forest[y][x] == Tile::Tree) as usize;
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y += step_down;
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x = (x + step_right) % width;
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}
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return trees;
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}
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fn main() {
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let forest = parse_input(&read_input());
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let p1 = count_trees(&forest, STEP_RIGHT[1], STEP_DOWN[1]);
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println!("Part 1: {}", p1);
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let p2 = count_all_paths(&forest);
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println!("Part 2: {}", p2);
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}
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mod tests {
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use super::*;
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use test;
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const INPUT: &str = "..##.......
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#...#...#..
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.#....#..#.
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..#.#...#.#
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.#...##..#.
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..#.##.....
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.#.#.#....#
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.#........#
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#.##...#...
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#...##....#
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.#..#...#.#";
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#[test]
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fn part1_test() {
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let forest = parse_input(INPUT);
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assert_eq!(
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count_trees(&forest, STEP_RIGHT[1], STEP_DOWN[1]),
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7
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);
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}
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#[test]
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fn part2_test() {
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let forest = parse_input(INPUT);
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assert_eq!(
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count_all_paths(&forest),
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336
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);
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}
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}
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