1 files changed, 102 insertions, 0 deletions
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
+    );
+}