day(18): make the guess of dimensions better

Signed-off-by: Matej Focko <me@mfocko.xyz>

src/bin/day18.rs

@@ -7,7 +7,7 @@ type Output1 = usize;
 type Output2 = Output1;
 
 struct Step {
-    direction: Vector2D<isize>,
+    _direction: (isize, isize),
     count: isize,
     color: String,
 }
@@ -18,11 +18,11 @@ impl FromStr for Step {
     fn from_str(s: &str) -> Result<Self, Self::Err> {
         let mut parts = s.split_ascii_whitespace();
 
-        let direction = match parts.next().unwrap() {
-            "U" => Vector2D::new(0, -1),
-            "D" => Vector2D::new(0, 1),
-            "L" => Vector2D::new(-1, 0),
-            "R" => Vector2D::new(1, 0),
+        let _direction = match parts.next().unwrap() {
+            "U" => (0, -1),
+            "D" => (0, 1),
+            "L" => (-1, 0),
+            "R" => (1, 0),
             _ => unreachable!(),
         };
 
@@ -34,13 +34,19 @@ impl FromStr for Step {
             .to_owned();
 
         Ok(Step {
-            direction,
+            _direction,
             count,
             color,
         })
     }
 }
 
+impl Step {
+    fn direction(&self) -> Vector2D<isize> {
+        Vector2D::new(self._direction.0, self._direction.1)
+    }
+}
+
 fn flood_fill(m: &mut [Vec<char>], start: Vector2D<isize>, original: char, fill: char) -> usize {
     let mut filled_in = 0;
 
@@ -75,22 +81,46 @@ impl Solution<Output1, Output2> for Day18 {
     }
 
     fn part_1(&mut self) -> Output1 {
-        let n = self.plan.iter().map(|s| s.count).sum::<isize>();
+        let (min_x, max_x, min_y, max_y) = self.plan.iter().fold((0, 0, 0, 0), |dimensions, s| {
+            let (mut lx, mut ux, mut ly, mut uy) = dimensions;
 
-        let mut map = vec![vec!['.'; 2 * n as usize]; 2 * n as usize];
-        let mut position = Vector2D::new(n, n);
+            match s._direction {
+                (0, 1) => uy += s.count,
+                (0, -1) => ly += s.count,
+                (1, 0) => ux += s.count,
+                (-1, 0) => lx += s.count,
+                _ => unreachable!(),
+            }
 
+            (lx, ux, ly, uy)
+        });
+        let (width, height) = (min_x + max_x + 1, min_y + max_y + 1);
+
+        debug!("Dimensions: {}×{}", width, height);
+
+        let mut map = vec![vec!['.'; width as usize]; height as usize];
+        let mut position = Vector2D::new(min_x, min_y);
+        // debug!("Initial position: {:?}", position);
+
+        // let (mut min_x, mut max_x, mut min_y, mut max_y) = (isize::MAX, isize::MIN, isize::MAX, isize::MIN);
         for s in &self.plan {
+            let direction = s.direction();
             for _ in 0..s.count {
+                // min_x = std::cmp::min(min_x, position.x());
+                // max_x = std::cmp::max(max_x, position.x());
+                // min_y = std::cmp::min(min_y, position.y());
+                // max_y = std::cmp::max(max_y, position.y());
+
                 map[position] = '#';
-                position = position + s.direction;
+                position = position + direction;
             }
         }
+        // debug!("x ∈ ⟨{} ; {}⟩\ty ∈ ⟨{} ; {}⟩", min_x, max_x, min_y, max_y);
 
         flood_fill(&mut map, Vector2D::new(0, 0), '.', '+');
 
         while let Some((y, x)) =
-            iproduct!(0..2 * n as usize, 0..2 * n as usize).find(|&(y, x)| map[y][x] == '.')
+            iproduct!(0..height as usize, 0..width as usize).find(|&(y, x)| map[y][x] == '.')
         {
             flood_fill(&mut map, Vector2D::new(x as isize, y as isize), '.', '#');
         }