From 148112498bd4c89e132c1014c19d19631b6fa537 Mon Sep 17 00:00:00 2001
From: Justin Wernick <justin@worthe-it.co.za>
Date: Thu, 14 Dec 2023 19:37:49 +0200
Subject: Day 10 part 2

---
 2023/src/bin/day_10.rs | 122 ++++++++++++++++++++++---------------------------
 1 file changed, 54 insertions(+), 68 deletions(-)

(limited to '2023/src/bin')

diff --git a/2023/src/bin/day_10.rs b/2023/src/bin/day_10.rs
index 33937b8..84d6327 100644
--- a/2023/src/bin/day_10.rs
+++ b/2023/src/bin/day_10.rs
@@ -83,41 +83,59 @@ impl Maze {
     fn count_blocks_inside_the_pipe_loop(&self) -> usize {
         let mut flood_fill_maze = FloodFillMaze::init_for_maze(&self);
 
+        let start_position = self.find_start();
+
         {
-            // flood fill the pipe loop
-            let mut position = self.find_start();
-            flood_fill_maze.fill_one(position, FloodFill::Pipe);
+            // fill the pipe loop
+            let mut position = start_position;
+            flood_fill_maze.fill(position, FloodFill::Pipe);
 
             let mut facing = self.find_start_facing(position);
             position = position.go(facing);
 
             while self.at(position) != Pipe::Start {
-                flood_fill_maze.fill_one(position, FloodFill::Pipe);
+                flood_fill_maze.fill(position, FloodFill::Pipe);
                 facing = self.at(position).exit_facing(facing).unwrap();
                 position = position.go(facing);
             }
         }
 
-        let (normal, start_pipe_position) = {
-            // flood fill from the boundary until I find a pipe loop piece
-            let mut position = Point { x: 0, y: 0 };
-            let mut found_pipes = Vec::new();
-
-            while found_pipes.len() == 0 {
-                found_pipes = flood_fill_maze
-                    .fill_flood(position, FloodFill::Outside)
-                    .into_iter()
-                    .filter(|(_, p)| self.at(*p).connections().len() == 2)
-                    .collect();
-                position = position.right();
+        for y in 0..self.0.len() {
+            for x in 0..self.0[y].len() {
+                if flood_fill_maze.0[y][x].is_none() {
+                    let trace_range = if y <= start_position.y {
+                        0..y
+                    } else {
+                        y + 1..self.0.len()
+                    };
+                    let mut outside = true;
+                    for trace_y in trace_range {
+                        if flood_fill_maze.0[trace_y][x] == Some(FloodFill::Pipe)
+                            && self
+                                .at(Point { x, y: trace_y })
+                                .crossed_by_vertical_hanging_right()
+                        {
+                            outside = !outside;
+                        }
+                    }
+                    flood_fill_maze.fill(
+                        Point { x, y },
+                        if outside {
+                            FloodFill::Outside
+                        } else {
+                            FloodFill::Inside
+                        },
+                    );
+                }
             }
-            found_pipes[0]
-        };
+        }
 
-        // use this to identify the inner side of the pipe
-        // trace along the inner side of the pipe, floor filling inside
-        // count the number of inner fills
-        todo!()
+        flood_fill_maze
+            .0
+            .iter()
+            .flat_map(|row| row.iter())
+            .filter(|x| **x == Some(FloodFill::Inside))
+            .count()
     }
 
     fn at(&self, p: Point) -> Pipe {
@@ -231,6 +249,19 @@ impl Pipe {
             },
         }
     }
+
+    fn crossed_by_vertical_hanging_right(&self) -> bool {
+        match self {
+            Pipe::Start => panic!("Undefined crossing over the start"),
+            Pipe::Nothing => false,
+            Pipe::DownLeft => false,
+            Pipe::DownRight => true,
+            Pipe::DownUp => false,
+            Pipe::LeftRight => true,
+            Pipe::UpLeft => false,
+            Pipe::UpRight => true,
+        }
+    }
 }
 
 impl Point {
@@ -282,54 +313,9 @@ impl FloodFillMaze {
         )
     }
 
-    fn fill_one(&mut self, point: Point, fill: FloodFill) {
-        if self.0[point.y][point.x].is_none() {
-            self.0[point.y][point.x] = Some(fill);
-        }
-    }
-
-    /// Returns a list of touched pipes, and the direction they were touched
-    /// from.
-    fn fill_flood(&mut self, point: Point, fill: FloodFill) -> Vec<(Direction, Point)> {
-        let mut pipes = Vec::new();
-
+    fn fill(&mut self, point: Point, fill: FloodFill) {
         if self.0[point.y][point.x].is_none() {
             self.0[point.y][point.x] = Some(fill);
-
-            if point.y > 0 {
-                let up = point.up();
-                if self.0[up.y][up.x] == Some(FloodFill::Pipe) {
-                    pipes.push((Direction::Up, up));
-                } else {
-                    pipes.append(&mut self.fill_flood(up, fill));
-                }
-            }
-            if point.y < self.0.len() - 1 {
-                let down = point.down();
-                if self.0[down.y][down.x] == Some(FloodFill::Pipe) {
-                    pipes.push((Direction::Down, down));
-                } else {
-                    pipes.append(&mut self.fill_flood(down, fill))
-                }
-            }
-            if point.x > 0 {
-                let left = point.left();
-                if self.0[left.y][left.x] == Some(FloodFill::Pipe) {
-                    pipes.push((Direction::Left, left));
-                } else {
-                    pipes.append(&mut self.fill_flood(left, fill))
-                };
-            }
-            if point.x < self.0[point.y].len() - 1 {
-                let right = point.right();
-                if self.0[right.y][right.x] == Some(FloodFill::Pipe) {
-                    pipes.push((Direction::Right, right));
-                } else {
-                    pipes.append(&mut self.fill_flood(right, fill))
-                }
-            }
         }
-
-        pipes
     }
 }
-- 
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