91 lines
2.7 KiB
Rust
91 lines
2.7 KiB
Rust
struct Tree {
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height: u8,
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visible: bool,
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scenic: usize,
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}
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struct Grid {
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width: usize,
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height: usize,
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trees: Vec<Tree>,
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}
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impl Grid {
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fn parse(str: &str) -> Self {
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let width = str.lines().next().unwrap().len();
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let height = str.lines().count();
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let trees = str
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.lines()
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.flat_map(|l| l.chars())
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.map(|c| Tree {
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height: (c as u32 - '0' as u32) as u8,
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visible: false,
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scenic: 0,
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})
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.collect();
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Self {
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width,
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height,
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trees,
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}
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}
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fn at_mut(&mut self, x: usize, y: usize) -> Option<&mut Tree> {
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if x >= self.width || y >= self.height {
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None
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} else {
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Some(&mut self.trees[y * self.width + x])
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}
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}
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fn scan_visibility(&mut self, xy: impl Iterator<Item = (usize, usize)>) {
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let mut max_height = 0;
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for (x, y) in xy {
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let tree = self.at_mut(x, y).unwrap();
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if tree.height >= max_height {
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tree.visible = true;
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max_height = tree.height + 1;
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}
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}
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}
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fn viewing_distance(&mut self, height: u8, xy: impl Iterator<Item = (usize, usize)>) -> usize {
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let mut count = 0;
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for (x, y) in xy {
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count += 1;
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let new_height = self.at_mut(x, y).unwrap().height;
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if new_height >= height {
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break;
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}
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}
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count
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}
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}
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pub fn solve(input: String) {
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let mut trees = Grid::parse(&input);
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for y in 0..trees.height {
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trees.scan_visibility((0..trees.width).map(|x| (x, y)));
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trees.scan_visibility((0..trees.width).map(|x| (x, y)).rev());
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}
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for x in 0..trees.width {
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trees.scan_visibility((0..trees.height).map(|y| (x, y)));
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trees.scan_visibility((0..trees.height).map(|y| (x, y)).rev());
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}
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let part1 = trees.trees.iter().filter(|t| t.visible).count();
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println!("Part 1: {part1}");
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for y in 0..trees.height {
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for x in 0..trees.width {
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let height = trees.at_mut(x, y).unwrap().height;
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let up = trees.viewing_distance(height, (0..y).rev().map(|y| (x, y)));
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let down = trees.viewing_distance(height, (y..trees.height).skip(1).map(|y| (x, y)));
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let left = trees.viewing_distance(height, (0..x).rev().map(|x| (x, y)));
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let right = trees.viewing_distance(height, (x..trees.width).skip(1).map(|x| (x, y)));
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trees.at_mut(x, y).unwrap().scenic = up * down * left * right;
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}
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}
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let part2 = trees.trees.iter().map(|t| t.scenic).max().unwrap();
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println!("Part 2: {part2}");
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}
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