Day 13a

Cargo.toml

@@ -15,5 +15,6 @@ members = [
     "day10",
     "day11",
     "day12",
+    "day13",
 ]
 

day13/Cargo.toml

@@ -0,0 +1,9 @@
+[package]
+name = "day13"
+version = "0.1.0"
+edition = "2021"
+
+[dependencies]
+aoc = { path = "../aoc" }
+color-eyre = "0.6.2"
+nom = "7.1.3"

day13/src/bin/day13a.rs

@@ -0,0 +1,109 @@
+// 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 std::collections::HashSet;
+use std::io::{stdin, BufRead};
+
+use day13::*;
+
+pub type Xy = (usize, usize);
+
+fn vecgrid2hashset(vecgrid: &VecGrid) -> (HashSet<Xy>, Xy) {
+    let size = (vecgrid[0].len(), vecgrid.len());
+    (
+        (0..size.1)
+            .flat_map(|y| (0..size.0).filter_map(move |x| vecgrid[y][x].then_some((x, y))))
+            .collect::<HashSet<Xy>>(),
+        size,
+    )
+}
+
+fn gridmatch_x(mirror: usize, size: &Xy, g: &HashSet<Xy>) -> bool {
+    let xmin = if 2 * mirror >= size.0 + 1 {
+        2 * mirror - size.0 + 2
+    } else {
+        0
+    };
+    for x in xmin..(mirror + 1) {
+        let xmirror = 2 * mirror + 1 - x;
+        if xmirror >= size.0 {
+            continue;
+        }
+        for y in 0..size.1 {
+            if g.contains(&(x, y)) != g.contains(&(xmirror, y)) {
+                return false;
+            }
+        }
+    }
+    true
+}
+
+fn gridmatch_y(mirror: usize, size: &Xy, g: &HashSet<Xy>) -> bool {
+    let ymin = if 2 * mirror >= size.1 + 1 {
+        2 * mirror - size.1 + 2
+    } else {
+        0
+    };
+    for y in ymin..(mirror + 1) {
+        let ymirror = 2 * mirror + 1 - y;
+        if ymirror >= size.1 {
+            continue;
+        }
+        for x in 0..size.0 {
+            if g.contains(&(x, y)) != g.contains(&(x, ymirror)) {
+                return false;
+            }
+        }
+    }
+    true
+}
+
+fn calc_summary(vecgrid: VecGrid) -> usize {
+    let (grid, size) = vecgrid2hashset(&vecgrid);
+    let max = std::cmp::max(size.0, size.1);
+    for mirror in (0..max - 1).rev() {
+        if mirror < size.0 - 1 && gridmatch_x(mirror, &size, &grid) {
+            return mirror + 1;
+        }
+        if mirror < size.1 - 1 && gridmatch_y(mirror, &size, &grid) {
+            return 100 * (mirror + 1);
+        }
+    }
+    panic!("no mirror found");
+}
+
+fn process(bufin: impl BufRead) -> Result<usize> {
+    let input = parser::parse(bufin)?;
+    Ok(input.into_iter().map(calc_summary).sum())
+}
+
+#[test]
+fn test() -> Result<()> {
+    assert_eq!(process(EXAMPLE.as_bytes())?, 405);
+    Ok(())
+}
+
+// #[test]
+// fn test2() -> Result<()> {
+//     pub const EXAMPLE: &str = "#..#...#.#..#
+// #..#####.####
+// #..######....
+// .##...####.#.
+// .##.##.#.####
+// #..#.###.##.#
+// .....###.#.#.
+// .##..##..##..
+// ....#.#####..
+// ....###..##.#
+// ....####.##.#
+// ";
+//     assert_eq!(process(EXAMPLE.as_bytes())?, 0405);
+//     Ok(())
+// }
+
+fn main() -> Result<()> {
+    color_eyre::install()?;
+    println!("{}", process(stdin().lock())?);
+    Ok(())
+}

day13/src/lib.rs

@@ -0,0 +1,61 @@
+// 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 color_eyre::{eyre::eyre, Result};
+
+pub const EXAMPLE: &str = "#.##..##.
+..#.##.#.
+##......#
+##......#
+..#.##.#.
+..##..##.
+#.#.##.#.
+
+#...##..#
+#....#..#
+..##..###
+#####.##.
+#####.##.
+..##..###
+#....#..#
+";
+
+pub type VecGrid = Vec<Vec<bool>>;
+
+pub mod parser {
+    use aoc::parser::*;
+
+    use super::*;
+
+    fn cell(input: &str) -> IResult<&str, bool> {
+        let (input, c) = character::one_of(".#")(input)?;
+        Ok((input, c == '#'))
+    }
+
+    fn line(input: &str) -> IResult<&str, Vec<bool>> {
+        let (input, cells) = multi::many1(cell)(input)?;
+        let (input, _) = character::newline(input)?;
+        Ok((input, cells))
+    }
+
+    fn grid(input: &str) -> IResult<&str, VecGrid> {
+        let (input, g) = multi::many1(line)(input)?;
+        Ok((input, g))
+    }
+
+    pub fn parse(mut bufin: impl BufRead) -> Result<Vec<VecGrid>> {
+        aoc::parse_with!(multi::separated_list1(character::newline, grid), bufin)
+    }
+}
+
+#[test]
+fn test() -> Result<()> {
+    let input = parser::parse(EXAMPLE.as_bytes())?;
+    assert_eq!(input.len(), 2);
+    assert_eq!(input[0].len(), 7);
+    assert_eq!(input[0][1].len(), 9);
+    assert_eq!(input[1].len(), 7);
+    assert_eq!(input[1][1].len(), 9);
+    Ok(())
+}