y2024d18

y2024/src/bin/d18.rs

@@ -0,0 +1,27 @@
+use std::{fs, time::Instant};
+
+use utils::time::get_elapsed_string;
+use y2024::days::d18;
+
+fn main() {
+    let now = Instant::now();
+    println!("Part 1:");
+    part1();
+    println!("Ran in {}", get_elapsed_string(now.elapsed()));
+    let now = Instant::now();
+    println!("Part 2:");
+    part2();
+    println!("Ran in {}", get_elapsed_string(now.elapsed()));
+}
+
+fn part1() {
+    let root = env!("CARGO_MANIFEST_DIR");
+    let content = fs::read_to_string(format!("{root}/resources/18_input.txt")).unwrap();
+    println!("{}", d18::process_part1(&content));
+}
+
+fn part2() {
+    let root = env!("CARGO_MANIFEST_DIR");
+    let content = fs::read_to_string(format!("{root}/resources/18_input.txt")).unwrap();
+    println!("{}", d18::process_part2(&content));
+}

y2024/src/days/d18.rs

@@ -0,0 +1,294 @@
+use std::{collections::HashSet, error::Error};
+
+use itertools::Itertools;
+
+pub fn process_part1(input: &str) -> u32 {
+    let falling_bytes = &input
+        .lines()
+        .map(|line| {
+            let (x, y) = line.split_once(",").unwrap();
+            (x.parse().unwrap(), y.parse().unwrap())
+        })
+        .collect_vec()[..1024];
+    let y_walls = vec![GridTile::Wall; 73];
+    let mut inner_rows = vec![GridTile::Path; 71];
+    inner_rows.insert(0, GridTile::Wall);
+    inner_rows.push(GridTile::Wall);
+    let mut grid = vec![inner_rows; 71];
+    grid.insert(0, y_walls.clone());
+    grid.push(y_walls);
+    simulate(grid, falling_bytes).unwrap()
+}
+
+fn simulate(mut grid: Vec<Vec<GridTile>>, falling_bytes: &[(usize, usize)]) -> Option<u32> {
+    grid[1][1] = GridTile::Start;
+    let height = grid.len();
+    let width = grid[0].len();
+    grid[height - 2][width - 2] = GridTile::End;
+    falling_bytes.iter().for_each(|(x, y)| {
+        grid[*y + 1][*x + 1] = GridTile::Wall;
+    });
+    let mut visited = HashSet::new();
+    visited.insert((1, 1));
+    let mut next_paths = vec![MazeRunner {
+        coords: (1, 1),
+        visited: visited.clone(),
+        ..Default::default()
+    }];
+    let mut arrived: Vec<MazeRunner> = Vec::new();
+    while !next_paths.is_empty() {
+        next_paths = next_paths
+            .iter()
+            .map(|maze_runner| {
+                let mut paths = Vec::new();
+                if let Some(path) = maze_runner.get_next(&grid, Direction::Up) {
+                    paths.push(path);
+                }
+                if let Some(path) = maze_runner.get_next(&grid, Direction::Down) {
+                    paths.push(path);
+                }
+                if let Some(path) = maze_runner.get_next(&grid, Direction::Left) {
+                    paths.push(path);
+                }
+                if let Some(path) = maze_runner.get_next(&grid, Direction::Right) {
+                    paths.push(path);
+                }
+                paths
+            })
+            .collect_vec()
+            .concat();
+        for (idx, maze_runner) in next_paths.clone().iter().enumerate().rev() {
+            if maze_runner.visited.contains(&maze_runner.coords)
+                || visited.contains(&maze_runner.coords)
+            {
+                next_paths.remove(idx);
+                continue;
+            }
+            visited.insert(maze_runner.coords);
+            next_paths[idx].visited.insert(maze_runner.coords);
+            if maze_runner.state == State::Arrived {
+                let arrived_reindeer = next_paths.remove(idx);
+                arrived.push(arrived_reindeer);
+            }
+        }
+    }
+    //let visited = arrived
+    //    .iter()
+    //    .map(|reindeer| {
+    //        reindeer
+    //            .visited
+    //            .iter()
+    //            .map(|(coords, _)| coords)
+    //            .collect_vec()
+    //    })
+    //    .collect_vec()
+    //    .concat();
+    //visited.iter().unique().count()
+    arrived.sort_by(|a_runner, b_runner| a_runner.visited.len().cmp(&b_runner.visited.len()));
+    if let Some(arrived) = arrived.first() {
+        log_maze(&grid, arrived);
+        Some(arrived.visited.len() as u32 - 1)
+    } else {
+        None
+    }
+}
+
+pub fn process_part2(input: &str) -> String {
+    let falling_bytes = &input
+        .lines()
+        .map(|line| {
+            let (x, y) = line.split_once(",").unwrap();
+            (x.parse::<usize>().unwrap(), y.parse::<usize>().unwrap())
+        })
+        .collect_vec();
+    let y_walls = vec![GridTile::Wall; 73];
+    let mut inner_rows = vec![GridTile::Path; 71];
+    inner_rows.insert(0, GridTile::Wall);
+    inner_rows.push(GridTile::Wall);
+    let mut grid = vec![inner_rows; 71];
+    grid.insert(0, y_walls.clone());
+    grid.push(y_walls);
+    let mut num_bytes = 1025;
+    while simulate(grid.clone(), &falling_bytes[..num_bytes]).is_some() {
+        num_bytes += 1;
+    }
+    let (x, y) = falling_bytes[num_bytes - 1];
+    format!("{x},{y}")
+}
+
+#[derive(Debug, Clone, PartialEq, Eq)]
+enum Direction {
+    Up,
+    Down,
+    Left,
+    Right,
+}
+
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
+enum State {
+    #[default]
+    Going,
+    Arrived,
+}
+
+#[derive(Debug, Default, Clone, PartialEq, Eq)]
+struct MazeRunner {
+    coords: (usize, usize),
+    visited: HashSet<(usize, usize)>,
+    state: State,
+}
+
+impl MazeRunner {
+    fn get_next(&self, grid: &[Vec<GridTile>], direction: Direction) -> Option<MazeRunner> {
+        let tile = match direction {
+            Direction::Up => grid[self.coords.1 - 1][self.coords.0],
+            Direction::Down => grid[self.coords.1 + 1][self.coords.0],
+            Direction::Right => grid[self.coords.1][self.coords.0 + 1],
+            Direction::Left => grid[self.coords.1][self.coords.0 - 1],
+        };
+        let coords = match direction {
+            Direction::Up => (self.coords.0, self.coords.1 - 1),
+            Direction::Down => (self.coords.0, self.coords.1 + 1),
+            Direction::Left => (self.coords.0 - 1, self.coords.1),
+            Direction::Right => (self.coords.0 + 1, self.coords.1),
+        };
+        if tile == GridTile::Wall {
+            None
+        } else if tile == GridTile::End {
+            Some(MazeRunner {
+                state: State::Arrived,
+                coords,
+                ..self.clone()
+            })
+        } else {
+            Some(MazeRunner {
+                coords,
+                ..self.clone()
+            })
+        }
+    }
+}
+
+#[derive(Debug, Default, Clone, Copy, Hash, PartialEq, Eq)]
+enum GridTile {
+    Wall,
+    #[default]
+    Path,
+    Start,
+    End,
+}
+
+impl TryFrom<char> for GridTile {
+    type Error = Box<dyn Error>;
+
+    fn try_from(value: char) -> std::result::Result<GridTile, Box<dyn Error>> {
+        match value {
+            '#' => Ok(Self::Wall),
+            '.' => Ok(Self::Path),
+            'S' => Ok(Self::Start),
+            'E' => Ok(Self::End),
+            _ => Err(Box::from(format!("{value} is not a valid tile"))),
+        }
+    }
+}
+
+fn log_maze(grid: &[Vec<GridTile>], maze_runner: &MazeRunner) {
+    for (yidx, row) in grid.iter().enumerate() {
+        for (xidx, tile) in row.iter().enumerate() {
+            let contains = {
+                maze_runner.visited.contains(&(xidx, yidx))
+                    || maze_runner.visited.contains(&(xidx, yidx))
+                    || maze_runner.visited.contains(&(xidx, yidx))
+                    || maze_runner.visited.contains(&(xidx, yidx))
+            };
+            if contains && !(*tile == GridTile::Start || *tile == GridTile::End) {
+                print!("O");
+            } else if *tile == GridTile::Wall {
+                print!("#");
+            } else if *tile == GridTile::Path {
+                print!(".");
+            } else if *tile == GridTile::Start {
+                print!("S");
+            } else if *tile == GridTile::End {
+                print!("E");
+            }
+        }
+        println!();
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT: &str = "5,4
+4,2
+4,5
+3,0
+2,1
+6,3
+2,4
+1,5
+0,6
+3,3
+2,6
+5,1
+1,2
+5,5
+2,5
+6,5
+1,4
+0,4
+6,4
+1,1
+6,1
+1,0
+0,5
+1,6
+2,0";
+
+    #[test]
+    fn part1() {
+        let falling_bytes = &INPUT
+            .lines()
+            .map(|line| {
+                let (x, y) = line.split_once(",").unwrap();
+                (x.parse().unwrap(), y.parse().unwrap())
+            })
+            .collect_vec()[..12];
+        let y_walls = vec![GridTile::Wall; 9];
+        let mut inner_rows = vec![GridTile::Path; 7];
+        inner_rows.insert(0, GridTile::Wall);
+        inner_rows.push(GridTile::Wall);
+        let mut grid = vec![inner_rows; 7];
+        grid.insert(0, y_walls.clone());
+        grid.push(y_walls);
+        let result = simulate(grid, falling_bytes);
+        assert_eq!(result, Some(22));
+    }
+
+    #[test]
+    fn part2() {
+        let falling_bytes = INPUT
+            .lines()
+            .map(|line| {
+                let (x, y) = line.split_once(",").unwrap();
+                (x.parse::<usize>().unwrap(), y.parse::<usize>().unwrap())
+            })
+            .collect_vec();
+        let y_walls = vec![GridTile::Wall; 9];
+        let mut inner_rows = vec![GridTile::Path; 7];
+        inner_rows.insert(0, GridTile::Wall);
+        inner_rows.push(GridTile::Wall);
+        let mut grid = vec![inner_rows; 7];
+        grid.insert(0, y_walls.clone());
+        grid.push(y_walls);
+        let mut num_bytes = 12;
+        while simulate(grid.clone(), &falling_bytes[..num_bytes]).is_some() {
+            num_bytes += 1;
+        }
+        let (x, y) = falling_bytes[num_bytes - 1];
+        let result = format!("{x},{y}");
+        assert_eq!(result, "6,1".to_string());
+    }
+}

y2024/src/days/mod.rs

@@ -23,3 +23,5 @@ pub mod d15;
 pub mod d16;
 
 pub mod d17;
+
+pub mod d18;