Move the Grid type to the common library

src/bin/day4.rs

@@ -1,77 +1,27 @@
 use std::time::Instant;
 
-use aoc_2025::{load, print_res};
+use aoc_2025::{Grid, load, print_res};
 use bstr::{BString, ByteSlice};
 use color_eyre::eyre::ContextCompat;
 
-type Parsed = Grid;
+type Parsed = Grid<RollSlot>;
 
-pub struct Grid {
-    values: Vec<bool>,
-    line_len: usize,
-    col_len: usize,
+#[derive(PartialEq, Eq)]
+pub enum RollSlot {
+    Roll,
+    Space,
 }
 
-impl Grid {
-    fn get(&self, line: isize, col: isize) -> Option<bool> {
-        if line < 0 || col < 0 || line as usize >= self.line_len || col as usize >= self.col_len {
-            None
-        } else {
-            Some(self[(line as usize, col as usize)])
-        }
-    }
-
-    fn neighbours(&self, line: usize, col: usize) -> usize {
-        let mut sum = 0;
-        for l in -1..=1 {
-            for c in -1..=1 {
-                if l == 0 && c == 0 {
-                    continue;
-                }
-
-                if self
-                    .get(line as isize + l, col as isize + c)
-                    .unwrap_or(false)
-                {
-                    sum += 1
-                }
-            }
-        }
-        sum
-    }
-}
-
-impl std::ops::Index<(usize, usize)> for Grid {
-    type Output = bool;
-
-    fn index(&self, (line, col): (usize, usize)) -> &Self::Output {
-        &self.values[line * self.line_len + col]
-    }
-}
-
-impl std::ops::IndexMut<(usize, usize)> for Grid {
-    fn index_mut(&mut self, (line, col): (usize, usize)) -> &mut Self::Output {
-        &mut self.values[line * self.line_len + col]
-    }
-}
-
-impl std::fmt::Display for Grid {
+impl std::fmt::Display for RollSlot {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        for line in self.values.chunks_exact(self.line_len) {
-            line.iter().try_for_each(|v| {
-                write!(
-                    f,
-                    "{}",
-                    match v {
-                        true => '@',
-                        false => '.',
-                    }
-                )
-            })?;
-            writeln!(f)?;
-        }
-
-        Ok(())
+        write!(
+            f,
+            "{}",
+            match self {
+                RollSlot::Roll => '@',
+                RollSlot::Space => '.',
+            }
+        )
     }
 }
 
@@ -81,30 +31,27 @@ pub fn parsing(input: &BString) -> color_eyre::Result<Parsed> {
     let values: Vec<_> = input
         .iter()
         .filter(|&&v| v != b'\n')
-        .map(|&v| v == b'@')
+        .map(|&v| {
+            if v == b'@' {
+                RollSlot::Roll
+            } else {
+                RollSlot::Space
+            }
+        })
         .collect();
 
-    assert_eq!(
-        values.len() % line_len,
-        0,
-        "Line length does not divide the grid size"
-    );
-    Ok(Grid {
-        line_len,
-        col_len: values.len() / line_len,
-        values,
-    })
+    Ok(Grid::new(values, line_len))
 }
 
 #[inline(never)]
 pub fn part1(input: Parsed) {
     let mut count = 0;
 
-    for line in 0..input.line_len {
-        for col in 0..input.line_len {
-            if input[(line, col)] && input.neighbours(line, col) < 4 {
-                count += 1;
-            }
+    for (line, col) in input.coords() {
+        if input[(line, col)] == RollSlot::Roll
+            && input.neighbour_count_like(line, col, &RollSlot::Roll) < 4
+        {
+            count += 1;
         }
     }
 
@@ -117,13 +64,13 @@ pub fn part2(mut input: Parsed) {
 
     loop {
         let mut found = false;
-        for line in 0..input.line_len {
-            for col in 0..input.line_len {
-                if input[(line, col)] && input.neighbours(line, col) < 4 {
-                    input[(line, col)] = false;
-                    found = true;
-                    count += 1;
-                }
+        for (line, col) in input.coords() {
+            if input[(line, col)] == RollSlot::Roll
+                && input.neighbour_count_like(line, col, &RollSlot::Roll) < 4
+            {
+                input[(line, col)] = RollSlot::Space;
+                found = true;
+                count += 1;
             }
         }
 

src/lib.rs

@@ -6,6 +6,88 @@ use clap::Parser;
 
 pub mod tinyvec;
 
+pub struct Grid<T> {
+    values: Vec<T>,
+    line_len: usize,
+    col_len: usize,
+}
+
+impl<T> Grid<T> {
+    pub fn get(&self, line: isize, col: isize) -> Option<&T> {
+        if line < 0 || col < 0 || line as usize >= self.line_len || col as usize >= self.col_len {
+            None
+        } else {
+            Some(&self[(line as usize, col as usize)])
+        }
+    }
+
+    pub fn new(values: Vec<T>, line_len: usize) -> Self {
+        assert_eq!(
+            values.len() % line_len,
+            0,
+            "Line length does not divide the grid size"
+        );
+
+        Grid {
+            line_len,
+            col_len: values.len() / line_len,
+            values,
+        }
+    }
+
+    pub fn coords(&self) -> impl Iterator<Item = (usize, usize)> + use<T> {
+        let line_len = self.line_len;
+        let col_len = self.col_len;
+
+        (0..line_len).flat_map(move |l| (0..col_len).map(move |c| (l, c)))
+    }
+}
+
+impl<T: PartialEq + Eq> Grid<T> {
+    pub fn neighbour_count_like(&self, line: usize, col: usize, like: &T) -> usize {
+        let mut sum = 0;
+        for l in -1..=1 {
+            for c in -1..=1 {
+                if l == 0 && c == 0 {
+                    continue;
+                }
+
+                if let Some(v) = self.get(line as isize + l, col as isize + c)
+                    && v == like
+                {
+                    sum += 1
+                }
+            }
+        }
+        sum
+    }
+}
+
+impl<T> std::ops::Index<(usize, usize)> for Grid<T> {
+    type Output = T;
+
+    fn index(&self, (line, col): (usize, usize)) -> &Self::Output {
+        &self.values[line * self.line_len + col]
+    }
+}
+
+impl<T> std::ops::IndexMut<(usize, usize)> for Grid<T> {
+    fn index_mut(&mut self, (line, col): (usize, usize)) -> &mut Self::Output {
+        &mut self.values[line * self.line_len + col]
+    }
+}
+
+impl<T: std::fmt::Display> std::fmt::Display for Grid<T> {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        for line in self.values.chunks_exact(self.line_len) {
+            line.iter().try_for_each(|v| write!(f, "{v}"))?;
+            writeln!(f)?;
+        }
+
+        Ok(())
+    }
+}
+
 pub fn neighbours<L, C, T>(l: usize, c: usize, map: L) -> ArrayVec<(usize, usize), 4>
 where
     L: AsRef<[C]>,