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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,7 @@ | ||
| [package] | ||
| name = "AoC2023_23" | ||
| version = "0.1.0" | ||
| edition = "2021" | ||
|
|
||
| [dependencies] | ||
| aoc = { path = "../aoc" } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,259 @@ | ||
| #![allow(non_snake_case)] | ||
|
|
||
| use std::{ | ||
| collections::{HashMap, HashSet, VecDeque}, | ||
| str::FromStr, | ||
| }; | ||
|
|
||
| use aoc::{ | ||
| geometry::Direction, | ||
| grid::{Cell, CharGrid, Grid}, | ||
| Puzzle, | ||
| }; | ||
|
|
||
| #[derive(Debug, Eq, Hash, PartialEq)] | ||
| struct Edge { | ||
| cell: Cell, | ||
| distance: usize, | ||
| } | ||
|
|
||
| struct PathFinder<'a> { | ||
| grid: &'a CharGrid, | ||
| start: Cell, | ||
| end: Cell, | ||
| } | ||
|
|
||
| impl<'a> PathFinder<'a> { | ||
| fn new(grid: &'a CharGrid) -> Self { | ||
| Self { | ||
| grid, | ||
| start: Cell::at(0, 1), | ||
| end: Cell::at(grid.height() - 1, grid.width() - 2), | ||
| } | ||
| } | ||
|
|
||
| fn find_forks(&self) -> HashSet<Cell> { | ||
| let is_fork = |cell: &Cell| { | ||
| cell == &self.start | ||
| || cell == &self.end | ||
| || self.grid.get(cell) != '#' | ||
| && self | ||
| .grid | ||
| .capital_neighbours(cell) | ||
| .iter() | ||
| .filter(|n| self.grid.get(n) != '#') | ||
| .count() | ||
| > 2 | ||
| }; | ||
|
|
||
| self.grid.cells().filter(is_fork).collect::<HashSet<Cell>>() | ||
| } | ||
|
|
||
| fn build_graph( | ||
| &self, | ||
| forks: &HashSet<Cell>, | ||
| downward_slopes_only: bool, | ||
| ) -> HashMap<Cell, HashSet<Edge>> { | ||
| let mut graph = HashMap::<Cell, HashSet<Edge>>::new(); | ||
| for fork in forks { | ||
| let mut q = VecDeque::<(Cell, usize)>::new(); | ||
| q.push_back((*fork, 0_usize)); | ||
| let mut seen = HashSet::<Cell>::new(); | ||
| seen.insert(*fork); | ||
| while !q.is_empty() { | ||
| let (cell, distance) = q.pop_front().unwrap(); | ||
| if forks.contains(&cell) && cell != *fork { | ||
| graph | ||
| .entry(*fork) | ||
| .and_modify(|edges| { | ||
| edges.insert(Edge { cell, distance }); | ||
| }) | ||
| .or_insert( | ||
| vec![Edge { cell, distance }] | ||
| .into_iter() | ||
| .collect::<HashSet<Edge>>(), | ||
| ); | ||
| continue; | ||
| } | ||
| for d in Direction::capital() { | ||
| let n = match cell.try_at(d) { | ||
| Some(val) => val, | ||
| None => continue, | ||
| }; | ||
| if !self.grid.in_bounds(&n) { | ||
| continue; | ||
| } | ||
| let val = self.grid.get(&n); | ||
| if val == '#' | ||
| || (downward_slopes_only | ||
| && ['v', '^', '<', '>'].contains(&val) | ||
| && Direction::from_str(&val.to_string()).unwrap() | ||
| != d) | ||
| { | ||
| continue; | ||
| } | ||
| if !seen.contains(&n) { | ||
| seen.insert(n); | ||
| q.push_back((n, distance + 1)); | ||
| } | ||
| } | ||
| } | ||
| } | ||
| graph | ||
| } | ||
|
|
||
| fn find_longest( | ||
| graph: &HashMap<Cell, HashSet<Edge>>, | ||
| curr: Cell, | ||
| end: &Cell, | ||
| seen: &mut HashSet<Cell>, | ||
| ) -> i32 { | ||
| if curr == *end { | ||
| return 0; | ||
| } | ||
| let mut ans: i32 = -1_000_000_000; | ||
| seen.insert(curr); | ||
| for Edge { cell, distance } in graph.get(&curr).unwrap().iter() { | ||
| if seen.contains(cell) { | ||
| continue; | ||
| } | ||
| ans = ans.max( | ||
| *distance as i32 + Self::find_longest(graph, *cell, end, seen), | ||
| ); | ||
| } | ||
| seen.remove(&curr); | ||
| ans | ||
| } | ||
|
|
||
| fn find_longest_hike_length_with_only_downward_slopes(&self) -> u32 { | ||
| let forks = self.find_forks(); | ||
| let graph = self.build_graph(&forks, true); | ||
| Self::find_longest( | ||
| &graph, | ||
| self.start, | ||
| &self.end, | ||
| &mut HashSet::<Cell>::new(), | ||
| ) as u32 | ||
| } | ||
|
|
||
| fn find_longest_hike_length(&self) -> u32 { | ||
| let forks = self.find_forks(); | ||
| let graph = self.build_graph(&forks, false); | ||
| let dist_from_start = graph | ||
| .get(&self.start) | ||
| .unwrap() | ||
| .iter() | ||
| .nth(0) | ||
| .unwrap() | ||
| .distance; | ||
| let dist_to_end = graph | ||
| .get(&self.end) | ||
| .unwrap() | ||
| .iter() | ||
| .nth(0) | ||
| .unwrap() | ||
| .distance; | ||
| let new_start = graph | ||
| .iter() | ||
| .filter(|(_, edges)| { | ||
| edges.contains(&Edge { | ||
| cell: self.start, | ||
| distance: dist_from_start, | ||
| }) | ||
| }) | ||
| .map(|(cell, _)| cell) | ||
| .nth(0) | ||
| .unwrap(); | ||
| let new_end = graph | ||
| .iter() | ||
| .filter(|(_, edges)| { | ||
| edges.contains(&Edge { | ||
| cell: self.end, | ||
| distance: dist_to_end, | ||
| }) | ||
| }) | ||
| .map(|(cell, _)| cell) | ||
| .nth(0) | ||
| .unwrap(); | ||
| dist_from_start as u32 | ||
| + dist_to_end as u32 | ||
| + Self::find_longest( | ||
| &graph, | ||
| *new_start, | ||
| new_end, | ||
| &mut HashSet::<Cell>::new(), | ||
| ) as u32 | ||
| } | ||
| } | ||
|
|
||
| struct AoC2023_23; | ||
|
|
||
| impl AoC2023_23 {} | ||
|
|
||
| impl aoc::Puzzle for AoC2023_23 { | ||
| type Input = CharGrid; | ||
| type Output1 = u32; | ||
| type Output2 = u32; | ||
|
|
||
| aoc::puzzle_year_day!(2023, 23); | ||
|
|
||
| fn parse_input(&self, lines: Vec<String>) -> CharGrid { | ||
| CharGrid::from(&lines.iter().map(AsRef::as_ref).collect()) | ||
| } | ||
|
|
||
| fn part_1(&self, grid: &CharGrid) -> u32 { | ||
| PathFinder::new(grid) | ||
| .find_longest_hike_length_with_only_downward_slopes() | ||
| } | ||
|
|
||
| fn part_2(&self, grid: &CharGrid) -> u32 { | ||
| PathFinder::new(grid).find_longest_hike_length() | ||
| } | ||
|
|
||
| fn samples(&self) { | ||
| aoc::puzzle_samples! { | ||
| self, part_1, TEST, 94, | ||
| self, part_2, TEST, 154 | ||
| }; | ||
| } | ||
| } | ||
|
|
||
| fn main() { | ||
| AoC2023_23 {}.run(std::env::args()); | ||
| } | ||
|
|
||
| const TEST: &str = "\ | ||
| #.##################### | ||
| #.......#########...### | ||
| #######.#########.#.### | ||
| ###.....#.>.>.###.#.### | ||
| ###v#####.#v#.###.#.### | ||
| ###.>...#.#.#.....#...# | ||
| ###v###.#.#.#########.# | ||
| ###...#.#.#.......#...# | ||
| #####.#.#.#######.#.### | ||
| #.....#.#.#.......#...# | ||
| #.#####.#.#.#########v# | ||
| #.#...#...#...###...>.# | ||
| #.#.#v#######v###.###v# | ||
| #...#.>.#...>.>.#.###.# | ||
| #####v#.#.###v#.#.###.# | ||
| #.....#...#...#.#.#...# | ||
| #.#########.###.#.#.### | ||
| #...###...#...#...#.### | ||
| ###.###.#.###v#####v### | ||
| #...#...#.#.>.>.#.>.### | ||
| #.###.###.#.###.#.#v### | ||
| #.....###...###...#...# | ||
| #####################.# | ||
| "; | ||
|
|
||
| #[cfg(test)] | ||
| mod tests { | ||
| use super::*; | ||
|
|
||
| #[test] | ||
| pub fn samples() { | ||
| AoC2023_23 {}.samples(); | ||
| } | ||
| } |
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