feat: day 6

Cargo.toml

@@ -26,6 +26,7 @@ chrono = { version = "0.4.38", optional = true }
 dhat = { version = "0.3.3", optional = true }
 itertools = "0.13.0"
 pico-args = "0.5.0"
+rayon = "1.10.0"
 regex = "1.11.1"
 tinyjson = "2.5.1"
 

data/examples/06.txt

@@ -0,0 +1,10 @@
+....#.....
+.........#
+..........
+..#.......
+.......#..
+..........
+.#..^.....
+........#.
+#.........
+......#...

src/bin/06.rs

@@ -0,0 +1,88 @@
+use rayon::prelude::*;
+use std::collections::HashSet;
+
+advent_of_code::solution!(6);
+
+const DIRS: [(isize, isize); 4] = [(-1, 0), (0, 1), (1, 0), (0, -1)];
+
+fn in_bounds(map: &Vec<Vec<char>>, pos: (isize, isize)) -> bool {
+    pos.0 >= 0 && pos.1 >= 0 && pos.0 < map.len() as isize && pos.1 < map[0].len() as isize
+}
+
+fn check_map(map: &Vec<Vec<char>>, start: (isize, isize)) -> (bool, Vec<(isize, isize)>) {
+    let mut visited: HashSet<(isize, isize)> = HashSet::new();
+    let mut visited_dir: HashSet<((isize, isize), usize)> = HashSet::new();
+    let mut dir = 0;
+    let mut current = start;
+    loop {
+        if visited_dir.contains(&(current, dir)) {
+            return (true, Vec::new());
+        }
+        visited.insert(current);
+        visited_dir.insert((current, dir));
+        let next = (current.0 + DIRS[dir].0, current.1 + DIRS[dir].1);
+        if !in_bounds(map, next) {
+            return (false, visited.iter().map(|x| *x).collect());
+        }
+        if map[next.0 as usize][next.1 as usize] == '#' {
+            dir = (dir + 1) % 4;
+            continue;
+        }
+        current = next;
+    }
+}
+
+fn parse_input(input: &str) -> (Vec<Vec<char>>, (isize, isize)) {
+    let map: Vec<Vec<char>> = input.lines().map(|line| line.chars().collect()).collect();
+    let mut start: (isize, isize) = (0, 0);
+    for i in 0..map.len() {
+        for j in 0..map[i].len() {
+            if map[i][j] == '^' {
+                start = (i as isize, j as isize);
+            }
+        }
+    }
+    (map, start)
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let (map, start) = parse_input(input);
+    let (_, visited) = check_map(&map, start);
+    Some(visited.len() as u32)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let (map, start) = parse_input(input);
+    let (_, visited) = check_map(&map, start);
+    Some(
+        visited
+            .par_iter()
+            .filter(|pos| {
+                if pos.0 == start.0 && pos.1 == start.1 {
+                    false;
+                }
+                let mut map = map.clone();
+                map[pos.0 as usize][pos.1 as usize] = '#';
+                let (looped, _) = check_map(&map, start);
+                looped
+            })
+            .count() as u32,
+    )
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part_one() {
+        let result = part_one(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(41));
+    }
+
+    #[test]
+    fn test_part_two() {
+        let result = part_two(&advent_of_code::template::read_file("examples", DAY));
+        assert_eq!(result, Some(6));
+    }
+}