perf: flatten Grid inner repr to Vec<u8>

src/grid_vec/grid.rs

@@ -8,25 +8,45 @@ use super::Point;
 
 #[derive(Debug, Clone)]
 pub struct Grid {
-    grid: Vec<Vec<u8>>,
+    grid: Vec<u8>,
+    width: usize,
 }
 
 impl FromStr for Grid {
     type Err = ();
     fn from_str(s: &str) -> Result<Self, Self::Err> {
-        let grid = s.lines().map(|x| x.as_bytes().to_vec()).collect();
-        Ok(Self { grid })
+        let mut grid = Vec::with_capacity(s.len());
+        let mut width = None;
+
+        for line in s.lines() {
+            let w = line.len();
+
+            if width.is_none() {
+                width = Some(w);
+            }
+
+            if width.filter(|&x| x == w).is_none() {
+                panic!("all lines have to be of same length");
+            }
+
+            grid.extend(line.bytes());
+        }
+
+        Ok(Self {
+            grid,
+            width: width.unwrap(),
+        })
     }
 }
 
 impl Display for Grid {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        for row in self.grid.iter() {
-            for cell in row.iter() {
+        for (idx, cell) in self.grid.iter().enumerate() {
             write!(f, "{}", *cell as char)?;
-            }
+            if idx > 0 && idx % self.width == 0 {
                 writeln!(f)?;
             }
+        }
         Ok(())
     }
 }
@@ -34,33 +54,33 @@ impl Display for Grid {
 impl Index<Point> for Grid {
     type Output = u8;
     fn index(&self, index: Point) -> &Self::Output {
-        &self.grid[index.i][index.j]
+        &self.grid[index.i * self.width + index.j]
     }
 }
 
 impl IndexMut<Point> for Grid {
     fn index_mut(&mut self, index: Point) -> &mut Self::Output {
-        &mut self.grid[index.i][index.j]
+        &mut self.grid[index.i * self.width + index.j]
     }
 }
 
 impl Grid {
     pub fn find(&self, f: u8) -> Option<Point> {
-        let (i, j, _) = self
+        let n = self
             .grid
             .iter()
             .enumerate()
-            .flat_map(|(i, x)| x.iter().copied().enumerate().map(move |(j, y)| (i, j, y)))
-            .find(|x| x.2 == f)?;
+            .find(|&(_, &x)| x == f)
+            .map(|x| x.0)?;
 
-        Some(Point::new(i, j))
+        Some(Point::new(n / self.width, n % self.width))
     }
 
     pub fn get(&self, p: &Point) -> Option<&u8> {
-        self.grid.get(p.i).and_then(|r| r.get(p.j))
+        self.grid.get(p.i * self.width + p.j)
     }
 
     pub fn get_mut(&mut self, p: &Point) -> Option<&mut u8> {
-        self.grid.get_mut(p.i).and_then(|r| r.get_mut(p.j))
+        self.grid.get_mut(p.i * self.width + p.j)
     }
 }