Day 23a

Cargo.toml

@@ -25,5 +25,6 @@ members = [
     "day20",
     "day21",
     "day22",
+    "day23",
 ]
 

day23/Cargo.toml

@@ -0,0 +1,10 @@
+[package]
+name = "day23"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+aoc = { path = "../aoc" }
+color-eyre = "0.6.2"
+nom = "7.1.3"
+sqrid = "0.0.24"

day23/src/bin/day23a.rs

@@ -0,0 +1,63 @@
+// Copyright (C) 2023 Leandro Lisboa Penz <lpenz@lpenz.org>
+// This file is subject to the terms and conditions defined in
+// file 'LICENSE', which is part of this source code package.
+
+use day23::*;
+
+use std::collections::HashSet;
+
+pub type Sqrid = sqrid::sqrid_create!(141, 141, false);
+pub type Pos = sqrid::pos_create!(Sqrid);
+pub type Grid = sqrid::grid_create!(Sqrid, Cell);
+
+fn dfs(size: u16, grid: &Grid, pos: Pos, visited: &HashSet<Pos>, end: Pos, steps: usize) -> usize {
+    if pos == end {
+        return steps;
+    }
+    let pos_t = pos.tuple();
+    if pos_t.0 >= size || pos_t.1 >= size {
+        return 0;
+    }
+    if visited.contains(&pos) {
+        return 0;
+    }
+    if grid[pos] == Cell::Wall {
+        return 0;
+    }
+    let mut newvisited = visited.clone();
+    newvisited.insert(pos);
+    if let Cell::Slope(dir) = grid[pos] {
+        let Ok(newpos) = pos + dir else { return 0 };
+        dfs(size, grid, newpos, &newvisited, end, steps + 1)
+    } else {
+        Dir::iter::<false>()
+            .filter_map(|dir| {
+                (pos + dir)
+                    .ok()
+                    .map(|newpos| dfs(size, grid, newpos, &newvisited, end, steps + 1))
+            })
+            .max()
+            .unwrap_or(0)
+    }
+}
+
+fn process(size: u16, bufin: impl BufRead) -> Result<usize> {
+    let input = parser::parse(bufin)?;
+    let grid = Grid::try_from(input)?;
+    let start = Pos::try_from((1, 0))?;
+    assert_eq!(grid[start], Cell::Empty);
+    let end = Pos::try_from((size - 2, size - 1))?;
+    assert_eq!(grid[end], Cell::Empty);
+    let visited = Default::default();
+    Ok(dfs(size, &grid, start, &visited, end, 0))
+}
+
+#[test]
+fn test() -> Result<()> {
+    assert_eq!(process(23, EXAMPLE.as_bytes())?, 94);
+    Ok(())
+}
+
+fn main() -> Result<()> {
+    do_main(|| process(141, stdin().lock()))
+}

day23/src/lib.rs

@@ -0,0 +1,106 @@
+// Copyright (C) 2023 Leandro Lisboa Penz <lpenz@lpenz.org>
+// This file is subject to the terms and conditions defined in
+// file 'LICENSE', which is part of this source code package.
+
+pub use aoc::*;
+
+use std::fmt;
+
+pub const EXAMPLE: &str = "#.#####################
+#.......#########...###
+#######.#########.#.###
+###.....#.>.>.###.#.###
+###v#####.#v#.###.#.###
+###.>...#.#.#.....#...#
+###v###.#.#.#########.#
+###...#.#.#.......#...#
+#####.#.#.#######.#.###
+#.....#.#.#.......#...#
+#.#####.#.#.#########v#
+#.#...#...#...###...>.#
+#.#.#v#######v###.###v#
+#...#.>.#...>.>.#.###.#
+#####v#.#.###v#.#.###.#
+#.....#...#...#.#.#...#
+#.#########.###.#.#.###
+#...###...#...#...#.###
+###.###.#.###v#####v###
+#...#...#.#.>.>.#.>.###
+#.###.###.#.###.#.#v###
+#.....###...###...#...#
+#####################.#
+";
+
+pub use sqrid::Dir;
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub enum Cell {
+    #[default]
+    Empty,
+    Wall,
+    Slope(Dir),
+}
+
+impl TryFrom<char> for Cell {
+    type Error = Report;
+    fn try_from(c: char) -> Result<Self, Self::Error> {
+        match c {
+            '.' => Ok(Cell::Empty),
+            '#' => Ok(Cell::Wall),
+            '^' => Ok(Cell::Slope(Dir::N)),
+            '>' => Ok(Cell::Slope(Dir::E)),
+            'v' => Ok(Cell::Slope(Dir::S)),
+            '<' => Ok(Cell::Slope(Dir::W)),
+            other => Err(eyre!("invalid cell {}", other)),
+        }
+    }
+}
+
+impl From<&Cell> for char {
+    fn from(c: &Cell) -> Self {
+        match c {
+            Cell::Empty => '.',
+            Cell::Wall => '#',
+            Cell::Slope(Dir::N) => '^',
+            Cell::Slope(Dir::E) => '>',
+            Cell::Slope(Dir::S) => 'v',
+            Cell::Slope(Dir::W) => '<',
+            _ => unreachable!(),
+        }
+    }
+}
+
+impl fmt::Display for Cell {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(f, "{}", char::from(self))
+    }
+}
+
+pub mod parser {
+    use aoc::parser::*;
+
+    use super::*;
+
+    fn cell(input: &str) -> IResult<&str, Cell> {
+        let (input, c) = character::one_of(".#^>v<")(input)?;
+        Ok((input, Cell::try_from(c).unwrap()))
+    }
+
+    fn line(input: &str) -> IResult<&str, Vec<Cell>> {
+        let (input, cells) = multi::many1(cell)(input)?;
+        let (input, _) = character::newline(input)?;
+        Ok((input, cells))
+    }
+
+    pub fn parse(mut bufin: impl BufRead) -> Result<Vec<Vec<Cell>>> {
+        aoc::parse_with!(multi::many1(line), bufin)
+    }
+}
+
+#[test]
+fn test() -> Result<()> {
+    let input = parser::parse(EXAMPLE.as_bytes())?;
+    assert_eq!(input.len(), 23);
+    assert_eq!(input[0].len(), 23);
+    Ok(())
+}