day 23: done for now

aoc23/src/main.rs

@@ -1,4 +1,4 @@
-use std::collections::{HashMap, HashSet};
+use std::collections::HashMap;
 use std::error::Error;
 use std::io::{self, Read, Write};
 use std::time::Instant;
@@ -22,17 +22,17 @@ fn parse_input<T: AsRef<str>>(input: T) -> Vec<Vec<char>> {
 
 fn neighbors(pos: Coord, trails: &[Vec<char>], part2: bool) -> Vec<Coord> {
     let (x, y) = pos;
-    let possible = if !part2 {
+    let possible: &[_] = if !part2 {
         match trails[x][y] {
-            '.' => vec![(-1, 0), (1, 0), (0, -1), (0, 1)],
-            '>' => vec![(0, 1)],
-            '<' => vec![(0, -1)],
-            '^' => vec![(-1, 0)],
-            'v' => vec![(1, 0)],
+            '.' => &[(-1, 0), (1, 0), (0, -1), (0, 1)],
+            '>' => &[(0, 1)],
+            '<' => &[(0, -1)],
+            '^' => &[(-1, 0)],
+            'v' => &[(1, 0)],
             _ => return vec![],
         }
     } else if trails[x][y] != '#' {
-        vec![(-1, 0), (1, 0), (0, -1), (0, 1)]
+        &[(-1, 0), (1, 0), (0, -1), (0, 1)]
     } else {
         return vec![];
     };
@@ -55,7 +55,7 @@ fn neighbors(pos: Coord, trails: &[Vec<char>], part2: bool) -> Vec<Coord> {
 fn dfs_grid(
     pos: Coord,
     trails: &[Vec<char>],
-    visited: &mut HashSet<Coord>,
+    visited: &mut [Vec<bool>],
     part2: bool,
 ) -> Option<usize> {
     if pos.0 == trails.len() - 1 {
@@ -67,11 +67,12 @@ fn dfs_grid(
     } else {
         let mut count = 0;
         for next in neighbors(pos, trails, part2) {
-            if visited.insert(next) {
+            if !visited[next.0][next.1] {
+                visited[next.0][next.1] = true;
                 if let Some(remain) = dfs_grid(next, trails, visited, part2) {
                     count = count.max(1 + remain);
                 }
-                visited.remove(&next);
+                visited[next.0][next.1] = false;
             }
         }
         if count == 0 {
@@ -117,18 +118,18 @@ fn dfs_graph(
     pos: Coord,
     end: Coord,
     graph: &HashMap<Coord, Vec<(Coord, usize)>>,
-    visited: &mut HashSet<Coord>,
+    visited: &mut [Vec<bool>],
 ) -> Option<usize> {
     if pos == end {
         return Some(0);
     }
-    let neighbors = graph.get(&pos).unwrap();
-    neighbors
+    graph[&pos]
         .iter()
         .filter_map(|&(next, d)| {
-            if visited.insert(next) {
+            if !visited[next.0][next.1] {
+                visited[next.0][next.1] = true;
                 let d = dfs_graph(next, end, graph, visited).map(|r| r + d);
-                visited.remove(&next);
+                visited[next.0][next.1] = false;
                 d
             } else {
                 None
@@ -144,14 +145,41 @@ fn part1(trails: &[Vec<char>]) -> Result<usize> {
         0,
         (0..trails[0].len()).find(|&y| trails[0][y] == '.').unwrap(),
     );
-    let result = dfs_grid(start, trails, &mut HashSet::new(), false).unwrap();
+    let result = dfs_grid(
+        start,
+        trails,
+        &mut vec![vec![false; trails[0].len()]; trails.len()],
+        false,
+    )
+    .unwrap();
 
     writeln!(io::stdout(), "Part 1: {result}")?;
     writeln!(io::stdout(), "> Time elapsed is: {:?}", _start.elapsed())?;
     Ok(result)
 }
 
-fn part2(trails: &[Vec<char>]) -> Result<usize> {
+#[allow(dead_code)]
+fn part2_grid(trails: &[Vec<char>]) -> Result<usize> {
+    let _start = Instant::now();
+
+    let start = (
+        0,
+        (0..trails[0].len()).find(|&y| trails[0][y] == '.').unwrap(),
+    );
+    let result = dfs_grid(
+        start,
+        trails,
+        &mut vec![vec![false; trails[0].len()]; trails.len()],
+        true,
+    )
+    .unwrap();
+
+    writeln!(io::stdout(), "Part 2 with grid: {result}")?;
+    writeln!(io::stdout(), "> Time elapsed is: {:?}", _start.elapsed())?;
+    Ok(result)
+}
+
+fn part2_graph(trails: &[Vec<char>]) -> Result<usize> {
     let _start = Instant::now();
 
     let start = (
@@ -166,9 +194,15 @@ fn part2(trails: &[Vec<char>]) -> Result<usize> {
     );
     let mut graph = gen_graph(trails, true);
     prune_graph(&mut graph);
-    let result = dfs_graph(start, end, &graph, &mut HashSet::new()).unwrap();
+    let result = dfs_graph(
+        start,
+        end,
+        &graph,
+        &mut vec![vec![false; trails[0].len()]; trails.len()],
+    )
+    .unwrap();
 
-    writeln!(io::stdout(), "Part 2: {result}")?;
+    writeln!(io::stdout(), "Part 2 with graph: {result}")?;
     writeln!(io::stdout(), "> Time elapsed is: {:?}", _start.elapsed())?;
     Ok(result)
 }
@@ -179,7 +213,8 @@ fn main() -> Result<()> {
 
     let trails = parse_input(input);
     part1(&trails)?;
-    part2(&trails)?;
+    part2_graph(&trails)?;
+    // part2_grid(&trails)?;
     Ok(())
 }
 
@@ -210,14 +245,15 @@ fn example_input() {
 #####################.#";
     let trails = parse_input(input);
     assert_eq!(part1(&trails).unwrap(), 94);
-    assert_eq!(part2(&trails).unwrap(), 154);
+    assert_eq!(part2_graph(&trails).unwrap(), 154);
+    assert_eq!(part2_grid(&trails).unwrap(), 154);
 }
 
 #[test]
 fn real_input() {
     let input = std::fs::read_to_string("input/input.txt").unwrap();
     let trails = parse_input(input);
     assert_eq!(part1(&trails).unwrap(), 2394);
-    assert_eq!(part2(&trails).unwrap(), 6554);
-    assert_eq!(2, 2);
+    assert_eq!(part2_graph(&trails).unwrap(), 6554);
+    // assert_eq!(part2_grid(&trails).unwrap(), 6554);
 }