From 94d4fc2fc3a181bd79f92eb6d93c833e88e6e802 Mon Sep 17 00:00:00 2001
From: Jesse Luehrs <doy@tozt.net>
Date: Wed, 13 Dec 2023 00:57:17 -0500
Subject: day 13

---
 src/bin/2023/day13.rs | 102 ++++++++++++++++++++++++++++++++++++++++++++++++++
 src/bin/2023/main.rs  |   2 +
 2 files changed, 104 insertions(+)
 create mode 100644 src/bin/2023/day13.rs

(limited to 'src/bin')

diff --git a/src/bin/2023/day13.rs b/src/bin/2023/day13.rs
new file mode 100644
index 0000000..a5579b8
--- /dev/null
+++ b/src/bin/2023/day13.rs
@@ -0,0 +1,102 @@
+#![allow(dead_code)]
+#![allow(unused_variables)]
+
+use advent_of_code::prelude::*;
+
+enum Mirror {
+    Horizontal(usize),
+    Vertical(usize),
+}
+
+impl Mirror {
+    fn score(&self) -> usize {
+        match self {
+            Self::Horizontal(n) => 100 * n,
+            Self::Vertical(n) => *n,
+        }
+    }
+}
+
+fn find_mirror(pattern: &Grid<bool>, smudges: usize) -> Mirror {
+    'mirror: for row in pattern.each_row().skip(1) {
+        let mut found_smudges = 0;
+        for offset in 0..row.min(pattern.rows() - row.0).0 {
+            let a = pattern.row_vec(row + offset);
+            let b = pattern.row_vec(row - offset - 1);
+            found_smudges += a
+                .into_iter()
+                .zip(b.into_iter())
+                .filter(|(a, b)| a != b)
+                .count();
+            if found_smudges > smudges {
+                continue 'mirror;
+            }
+        }
+        if found_smudges != smudges {
+            continue 'mirror;
+        }
+        return Mirror::Horizontal(row.0);
+    }
+
+    'mirror: for col in pattern.each_col().skip(1) {
+        let mut found_smudges = 0;
+        for offset in 0..col.min(pattern.cols() - col.0).0 {
+            let a = pattern.col_vec(col + offset);
+            let b = pattern.col_vec(col - offset - 1);
+            found_smudges += a
+                .into_iter()
+                .zip(b.into_iter())
+                .filter(|(a, b)| a != b)
+                .count();
+            if found_smudges > smudges {
+                continue 'mirror;
+            }
+        }
+        if found_smudges != smudges {
+            continue 'mirror;
+        }
+        return Mirror::Vertical(col.0);
+    }
+
+    unreachable!()
+}
+
+pub fn parse(fh: File) -> Result<Vec<Grid<bool>>> {
+    let mut lines = parse::raw_lines(fh).peekable();
+    let mut grids = vec![];
+    while lines.peek().is_some() {
+        grids
+            .push(parse::grid(parse::chunk(&mut lines), |c, _, _| c == b'#'));
+    }
+    Ok(grids)
+}
+
+pub fn part1(patterns: Vec<Grid<bool>>) -> Result<i64> {
+    Ok(patterns
+        .into_iter()
+        .map(|pattern| find_mirror(&pattern, 0).score())
+        .sum::<usize>()
+        .try_into()
+        .unwrap())
+}
+
+pub fn part2(patterns: Vec<Grid<bool>>) -> Result<i64> {
+    Ok(patterns
+        .into_iter()
+        .map(|pattern| find_mirror(&pattern, 1).score())
+        .sum::<usize>()
+        .try_into()
+        .unwrap())
+}
+
+#[test]
+fn test() {
+    assert_eq!(
+        part1(parse(parse::data(2023, 13).unwrap()).unwrap()).unwrap(),
+        37975
+    );
+    assert_eq!(
+        part2(parse(parse::data(2023, 13).unwrap()).unwrap()).unwrap(),
+        32497
+    );
+}
diff --git a/src/bin/2023/main.rs b/src/bin/2023/main.rs
index 591fdc8..2ee1dc4 100644
--- a/src/bin/2023/main.rs
+++ b/src/bin/2023/main.rs
@@ -23,6 +23,7 @@ mod day9;
 mod day10;
 mod day11;
 mod day12;
+mod day13;
 // NEXT MOD
 
 #[paw::main]
@@ -41,6 +42,7 @@ fn main(opt: Opt) -> Result<()> {
         10 => advent_of_code::day!(2023, opt.day, opt.puzzle, day10),
         11 => advent_of_code::day!(2023, opt.day, opt.puzzle, day11),
         12 => advent_of_code::day!(2023, opt.day, opt.puzzle, day12),
+        13 => advent_of_code::day!(2023, opt.day, opt.puzzle, day13),
         // NEXT PART
         _ => panic!("unknown day {}", opt.day),
     }
-- 
cgit v1.2.3-54-g00ecf