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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,158 @@ | ||
| use if_chain::if_chain; | ||
| use std::cmp::Reverse; | ||
| use std::collections::{BTreeMap, BTreeSet, BinaryHeap}; | ||
|
|
||
| type YX = (usize, usize); | ||
|
|
||
| fn parse(data: &str) -> Option<(BTreeSet<YX>, YX, YX)> { | ||
| let mut maze = BTreeSet::new(); | ||
| let mut start = None; | ||
| let mut end = None; | ||
| for (y, line) in data.lines().enumerate() { | ||
| for (x, b) in line.bytes().enumerate() { | ||
| match b { | ||
| b'#' => { | ||
| maze.insert((y, x)); | ||
| } | ||
| b'S' => { | ||
| if start.replace((y, x)).is_some() { | ||
| return None; | ||
| } | ||
| } | ||
| b'E' => { | ||
| if end.replace((y, x)).is_some() { | ||
| return None; | ||
| } | ||
| } | ||
| _ => {} | ||
| } | ||
| } | ||
| } | ||
| Some((maze, start?, end?)) | ||
| } | ||
|
|
||
| pub fn part1(data: &str) -> Option<usize> { | ||
| let (maze, start, end) = parse(data)?; | ||
| let mut queue: BinaryHeap<_> = [(Reverse(0), start, (0, 1))].into(); | ||
| let mut visited = BTreeSet::new(); | ||
| while let Some((Reverse(score), (y, x), (dy, dx))) = queue.pop() { | ||
| if !visited.insert(((y, x), (dy, dx))) { | ||
| continue; | ||
| } | ||
| if (y, x) == end { | ||
| return Some(score); | ||
| } | ||
| for (score, (dy, dx)) in [ | ||
| (score + 1, (dy, dx)), | ||
| (score + 1001, (-dx, dy)), | ||
| (score + 1001, (dx, -dy)), | ||
| ] { | ||
| if_chain! { | ||
| if let Some(y) = y.checked_add_signed(dy); | ||
| if let Some(x) = x.checked_add_signed(dx); | ||
| if !maze.contains(&(y, x)); | ||
| then { | ||
| queue.push((Reverse(score), (y, x), (dy, dx))); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| None | ||
| } | ||
|
|
||
| pub fn part2(data: &str) -> Option<usize> { | ||
| let (maze, start, end) = parse(data)?; | ||
| let mut best = None; | ||
| let mut acc = BTreeSet::new(); | ||
| let mut queue: BinaryHeap<(_, _, _, BTreeSet<_>)> = | ||
| [(Reverse(0), start, (0, 1), [start].into())].into(); | ||
| let mut visited = BTreeMap::new(); | ||
| while let Some((Reverse(score), (y, x), (dy, dx), mut path)) = queue.pop() { | ||
| if best.filter(|best| *best < score).is_some() { | ||
| break; | ||
| } | ||
| if *visited.entry(((y, x), (dy, dx))).or_insert(score) < score { | ||
| continue; | ||
| } | ||
| if (y, x) == end { | ||
| best = Some(score); | ||
| acc.append(&mut path); | ||
| continue; | ||
| } | ||
| for (score, (dy, dx)) in [ | ||
| (score + 1, (dy, dx)), | ||
| (score + 1001, (-dx, dy)), | ||
| (score + 1001, (dx, -dy)), | ||
| ] { | ||
| if_chain! { | ||
| if let Some(y) = y.checked_add_signed(dy); | ||
| if let Some(x) = x.checked_add_signed(dx); | ||
| if !maze.contains(&(y, x)); | ||
| then { | ||
| let mut path = path.clone(); | ||
| if path.insert((y, x)) { | ||
| queue.push((Reverse(score), (y, x), (dy, dx), path)); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| Some(acc.len()) | ||
| } | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
| use indoc::indoc; | ||
| use pretty_assertions::assert_eq; | ||
|
|
||
| static EXAMPLE_1: &str = indoc! {" | ||
| ############### | ||
| #.......#....E# | ||
| #.#.###.#.###.# | ||
| #.....#.#...#.# | ||
| #.###.#####.#.# | ||
| #.#.#.......#.# | ||
| #.#.#####.###.# | ||
| #...........#.# | ||
| ###.#.#####.#.# | ||
| #...#.....#.#.# | ||
| #.#.#.###.#.#.# | ||
| #.....#...#.#.# | ||
| #.###.#.#.#.#.# | ||
| #S..#.....#...# | ||
| ############### | ||
| "}; | ||
|
|
||
| static EXAMPLE_2: &str = indoc! {" | ||
| ################# | ||
| #...#...#...#..E# | ||
| #.#.#.#.#.#.#.#.# | ||
| #.#.#.#...#...#.# | ||
| #.#.#.#.###.#.#.# | ||
| #...#.#.#.....#.# | ||
| #.#.#.#.#.#####.# | ||
| #.#...#.#.#.....# | ||
| #.#.#####.#.###.# | ||
| #.#.#.......#...# | ||
| #.#.###.#####.### | ||
| #.#.#...#.....#.# | ||
| #.#.#.#####.###.# | ||
| #.#.#.........#.# | ||
| #.#.#.#########.# | ||
| #S#.............# | ||
| ################# | ||
| "}; | ||
|
|
||
| #[test] | ||
| fn part1_examples() { | ||
| assert_eq!(Some(7036), part1(EXAMPLE_1)); | ||
| assert_eq!(Some(11048), part1(EXAMPLE_2)); | ||
| } | ||
|
|
||
| #[test] | ||
| fn part2_examples() { | ||
| assert_eq!(Some(45), part2(EXAMPLE_1)); | ||
| assert_eq!(Some(64), part2(EXAMPLE_2)); | ||
| } | ||
| } |
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