johannes/advent-of-rust-2024
1
0
Fork 0
Code Activity

day 16 part 2

Browse Source
This commit is contained in:
Johannes
2024-12-16 12:47:16 +01:00
parent fd3629acfd
commit fbc80cac85
1 changed files with 47 additions and 8 deletions
Download Patch File Download Diff File Expand all files Collapse all files

55
src/day16.rs
View File

@@ -3,6 +3,8 @@ use std::{
fs::read_to_string, fs::read_to_string,
}; };
use itertools::Itertools;
use crate::utils::grid::{Coord, Grid}; use crate::utils::grid::{Coord, Grid};
pub fn day_main() { pub fn day_main() {
@@ -31,7 +33,7 @@ impl Dir {
} }
} }
struct Step(Coord, Dir, usize); struct Step(Coord, Dir, usize, Vec<Coord>);
impl Ord for Step { impl Ord for Step {
fn cmp(&self, other: &Self) -> std::cmp::Ordering { fn cmp(&self, other: &Self) -> std::cmp::Ordering {
@@ -57,8 +59,8 @@ fn part1(input: &str) -> RiddleResult {
let end = maze.entries().find(|(_p, c)| **c == 'E').unwrap().0; let end = maze.entries().find(|(_p, c)| **c == 'E').unwrap().0;
let mut visited = HashMap::<(Coord, Dir), usize>::new(); let mut visited = HashMap::<(Coord, Dir), usize>::new();
let mut stack: BinaryHeap<Step> = BinaryHeap::new(); let mut stack: BinaryHeap<Step> = BinaryHeap::new();
stack.push(Step(start, E, 0)); stack.push(Step(start, E, 0, vec![]));
while let Some(Step(np, nd, cost)) = stack.pop() { while let Some(Step(np, nd, cost, _)) = stack.pop() {
if visited.contains_key(&(np, nd)) { if visited.contains_key(&(np, nd)) {
continue; continue;
} }
@@ -68,7 +70,7 @@ fn part1(input: &str) -> RiddleResult {
} }
for d in nd.nexts() { for d in nd.nexts() {
if !visited.contains_key(&(np, d)) { if !visited.contains_key(&(np, d)) {
stack.push(Step(np, d, cost + 1000)); stack.push(Step(np, d, cost + 1000, vec![]));
} }
} }
let forward = match nd { let forward = match nd {
@@ -78,14 +80,51 @@ fn part1(input: &str) -> RiddleResult {
W => (np.0 - 1, np.1), W => (np.0 - 1, np.1),
}; };
if maze[forward] != '#' && !visited.contains_key(&(forward, nd)) { if maze[forward] != '#' && !visited.contains_key(&(forward, nd)) {
stack.push(Step(forward, nd, cost + 1)); stack.push(Step(forward, nd, cost + 1, vec![]));
} }
} }
panic!("no path found") panic!("no path found")
} }
fn part2(_input: &str) -> RiddleResult { fn part2(input: &str) -> RiddleResult {
0 use Dir::*;
let maze = Grid::parse(input);
let start = maze.entries().find(|(_p, c)| **c == 'S').unwrap().0;
let end = maze.entries().find(|(_p, c)| **c == 'E').unwrap().0;
let mut visited = HashMap::<(Coord, Dir), usize>::new();
let mut stack: BinaryHeap<Step> = BinaryHeap::new();
stack.push(Step(start, E, 0, vec![]));
let mut best: Option<usize> = None;
let mut visited_by_best: Vec<Coord> = vec![start, end];
while let Some(Step(np, nd, cost, mut pred)) = stack.pop() {
if let Some(b) = best {
if b < cost {
break; // can't reach the end point with best cost anymore
}
}
visited.insert((np, nd), cost);
if np == end {
best = Some(cost);
visited_by_best.append(&mut pred);
}
pred.push(np);
for d in nd.nexts() {
if !visited.contains_key(&(np, d)) {
stack.push(Step(np, d, cost + 1000, pred.clone()));
}
}
let forward = match nd {
N => (np.0, np.1 - 1),
E => (np.0 + 1, np.1),
S => (np.0, np.1 + 1),
W => (np.0 - 1, np.1),
};
if maze[forward] != '#' && !visited.contains_key(&(forward, nd)) {
stack.push(Step(forward, nd, cost + 1, pred));
}
}
visited_by_best.into_iter().unique().count()
} }
#[cfg(test)] #[cfg(test)]
@@ -116,6 +155,6 @@ mod test {
#[test] #[test]
fn test2() { fn test2() {
assert_eq!(part2(TEST_INPUT), 0); assert_eq!(part2(TEST_INPUT), 45);
} }
} }