day16: problem 2 solution

16/src/main.rs

@@ -47,16 +47,6 @@ impl Display for FromDirection {
     }
 }
 
-struct Tile {
-    kind: char,
-}
-
-impl From<char> for Tile {
-    fn from(c: char) -> Self {
-        Tile { kind: c }
-    }
-}
-
 struct Contraption {
     tiles: Vec<Vec<char>>,
 }
@@ -66,8 +56,42 @@ struct VisitState {
     visited_rays: HashSet<((i64, i64), FromDirection)>,
 }
 
+impl VisitState {
+    fn score(&self) -> u64 {
+        self.energized.iter().flatten().filter(|c| **c).count() as u64
+    }
+    fn dump(&self) {
+        println!("Score {}:", self.score());
+        for line in &self.energized {
+            println!(
+                "  {}",
+                String::from_iter(line.iter().map(|b| if *b { '#' } else { '.' }))
+            );
+        }
+    }
+}
+
+
 impl Contraption {
     fn cast_ray<'a>(
+        &'a mut self,
+        state: &'a mut VisitState,
+        pos: (i64, i64),
+        dir: FromDirection,
+    ) {
+        let mut new_rays = self.cast_ray_inner(state, pos, dir);
+
+        loop {
+            new_rays = new_rays
+                .iter()
+                .flat_map(|(pos, dir)| self.cast_ray_inner(state, *pos, *dir))
+                .collect();
+            if new_rays.len() == 0 {
+                break;
+            }
+        }
+    }
+    fn cast_ray_inner<'a>(
         &'a mut self,
         state: &'a mut VisitState,
         mut pos: (i64, i64),
@@ -148,42 +172,52 @@ impl<T: BufRead> From<Lines<T>> for Contraption {
     }
 }
 
-fn dump_state(state: &Vec<Vec<bool>>) {
-    for line in state {
-        println!(
-            "{}",
-            String::from_iter(line.iter().map(|b| if *b { '#' } else { '.' }))
-        );
-    }
-}
-
 // PROBLEM 1 solution
 
 fn problem1<T: BufRead>(input: Lines<T>) -> u64 {
     let mut contraption = Contraption::from(input);
     let mut state = contraption.empty_state();
 
-    let mut new_rays = contraption.cast_ray(&mut state, (0, 0), FromDirection::Left);
+    contraption.cast_ray(&mut state, (0,0), FromDirection::Left);
-    for ray in &new_rays {
-        println!("  {:?}", ray);
-    }
-
-    loop {
-        new_rays = new_rays
-            .iter()
-            .flat_map(|(pos, dir)| contraption.cast_ray(&mut state, *pos, *dir))
-            .collect();
-        if new_rays.len() == 0 {
-            break;
-        }
-    }
 
     state.energized.iter().flatten().filter(|c| **c).count() as u64
 }
 
 // PROBLEM 2 solution
 fn problem2<T: BufRead>(input: Lines<T>) -> u64 {
-    0
+    let mut contraption = Contraption::from(input);
+    let mut max_tiles = 0u64;
+
+    for y in 0..contraption.tiles.len() as i64 {
+        let mut left_state = contraption.empty_state();
+        contraption.cast_ray(&mut left_state, (0, y), FromDirection::Left);
+        let mut right_state = contraption.empty_state();
+        contraption.cast_ray(
+            &mut right_state,
+            (contraption.tiles[0].len() as i64 - 1, y),
+            FromDirection::Right,
+        );
+        max_tiles = std::cmp::max(
+            max_tiles,
+            std::cmp::max(left_state.score(), right_state.score()),
+        );
+    }
+    for x in 0..contraption.tiles[0].len() as i64 {
+        let mut top_state = contraption.empty_state();
+        contraption.cast_ray(&mut top_state, (x, 0), FromDirection::Above);
+        let mut bottom_state = contraption.empty_state();
+        contraption.cast_ray(
+            &mut bottom_state,
+            (x, contraption.tiles.len() as i64 - 1),
+            FromDirection::Below,
+        );
+        max_tiles = std::cmp::max(
+            max_tiles,
+            std::cmp::max(top_state.score(), bottom_state.score()),
+        );
+    }
+
+    max_tiles
 }
 
 #[cfg(test)]