10 rust

1 files changed, 69 insertions, 40 deletions

diff --git a/10/rust/src/main.rs b/10/rust/src/main.rs
index 7c0c3fe..7afe2e4 100644
--- a/10/rust/src/main.rs
+++ b/10/rust/src/main.rs
@@ -1,69 +1,98 @@
 use std::io::BufRead;
 
+#[derive(Debug)]
 struct Grid(Vec<String>);
 
 impl Grid {
     fn at(&self, x: isize, y: isize) -> char {
-        return self.0[y as usize].chars().nth(x as usize).unwrap();
+        if x < 0 || y < 0 {
+            return '\0';
+        }
+        let y = y as usize;
+        let x = x as usize;
+        if y >= self.0.len() || x >= self.0[y].len() {
+            return '\0';
+        }
+        return self.0[y].chars().nth(x).unwrap();
+    }
+
+    fn set(&mut self, x: isize, y: isize, c: char) {
+        let y = y as usize;
+        let x = x as usize;
+        self.0[y].replace_range(x..x + 1, &c.to_string());
+    }
+
+    fn flood(&mut self, x: isize, y: isize) -> usize {
+        let v = match self.at(x, y) {
+            ' ' => 0,
+            '.' => 1,
+            _ => return 0
+        };
+        self.set(x, y, '#');
+        return v + self.flood(x + 1, y) +
+        self.flood(x - 1, y) +
+        self.flood(x, y + 1) + 
+        self.flood(x, y - 1);
+    }
+
+    fn traverse(&self, expanded: &mut Grid, start_x: isize, start_y: isize) {
+        let mut x = start_x;
+        let mut y = start_y;
+        let mut dir_x = 0isize;
+        let mut dir_y = 0isize;
+
+        if "-LF".contains(self.at(x - 1, y)) {
+            dir_x = -1;
+        } else if "-J7".contains(self.at(x + 1, y)) {
+            dir_x = 1;
+        } else if "|7F".contains(self.at(x, y - 1)) {
+            dir_y = -1;
+        } else if "|JL".contains(self.at(x, y + 1)) {
+            dir_y = 1;
+        } else {
+            panic!("no valid adjacent pipe found");
+        }
+
+        loop {
+            expanded.set(x * 2, y * 2, '#');
+            expanded.set(x * 2 + dir_x, y * 2 + dir_y, '#');
+            x += dir_x;
+            y += dir_y;
+            match self.at(x, y) {
+                '-' | '|' => (),
+                '7' | 'L' => (dir_x, dir_y) = (dir_y, dir_x),
+                'F' | 'J' => (dir_x, dir_y) = (-dir_y, -dir_x),
+                'S' => break,
+                _ => unreachable!(),
+            }
+        }
     }
 }
 
 fn main() {
-    let mut grid: Grid = Grid(vec![]);
+    let mut grid = Grid(vec![]);
 
     for line in std::io::stdin().lock().lines() {
         grid.0.push(line.unwrap());
     }
 
+    let mut expanded = Grid(vec![]);
     let mut start_x = 0;
     let mut start_y = 0;
-    'outer: for (y, line) in grid.0.iter().enumerate() {
+    for (y, line) in grid.0.iter().enumerate() {
         for (x, c) in line.chars().enumerate() {
             if c == 'S' {
                 start_x = x;
                 start_y = y;
-                break 'outer;
             }
         }
+        expanded.0.push(". ".repeat(line.len()));
+        expanded.0.push("  ".repeat(line.len()));
     }
     assert!(start_x != 0);
     assert!(start_y != 0);
 
-    println!(
-        "{}",
-        traverse(&grid, start_x as isize, start_y as isize) / 2
-    );
-}
-
-fn traverse(grid: &Grid, start_x: isize, start_y: isize) -> usize {
-    let mut x = start_x;
-    let mut y = start_y;
-    let mut dir_x = 0isize;
-    let mut dir_y = 0isize;
-    let mut steps = 1;
+    grid.traverse(&mut expanded, start_x as isize, start_y as isize);
 
-    if "-LF".contains(grid.at(x - 1, y)) {
-        dir_x = -1;
-    } else if "-J7".contains(grid.at(x + 1, y)) {
-        dir_x = 1;
-    } else if "|7F".contains(grid.at(x, y - 1)) {
-        dir_y = -1;
-    } else if "|JL".contains(grid.at(x, y + 1)) {
-        dir_y = 1;
-    } else {
-        panic!("no valid adjacent pipe found");
-    }
-
-    loop {
-        steps += 1;
-        x += dir_x;
-        y += dir_y;
-        match grid.at(x, y) {
-            '-' | '|' => (),
-            '7' | 'L' => (dir_x, dir_y) = (dir_y, dir_x),
-            'F' | 'J' => (dir_x, dir_y) = (-dir_y, -dir_x),
-            'S' => return steps,
-            _ => unreachable!(),
-        }
-    }
+    println!("{}", expanded.flood(grid.0[0].len() as isize, grid.0.len() as isize));
 }