From 99cb590d6fa24ffc8e454d68d4d68038a98dcb07 Mon Sep 17 00:00:00 2001
From: Matej Focko <mfocko@redhat.com>
Date: Sun, 10 Dec 2023 17:45:24 +0100
Subject: [PATCH] day(10): refactor the part 2

Signed-off-by: Matej Focko <mfocko@redhat.com>
---
 src/bin/day10.rs | 107 ++++++++++++++++++++++++++++-------------------
 1 file changed, 64 insertions(+), 43 deletions(-)

diff --git a/src/bin/day10.rs b/src/bin/day10.rs
index 5f1b0fa..d1e42d2 100644
--- a/src/bin/day10.rs
+++ b/src/bin/day10.rs
@@ -1,10 +1,44 @@
-use std::{collections::VecDeque, fmt::Display, fmt::Write};
+use std::{
+    collections::{HashMap, VecDeque},
+    fmt::Display,
+    fmt::Write,
+};
 
 use aoc_2023::*;
 
 type Output1 = i32;
 type Output2 = Output1;
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
+enum Direction {
+    North,
+    East,
+    South,
+    West,
+}
+
+impl Direction {
+    fn direction_vector(&self) -> Vector2D<isize> {
+        match self {
+            Direction::North => Vector2D::new(0, -1),
+            Direction::East => Vector2D::new(1, 0),
+            Direction::South => Vector2D::new(0, 1),
+            Direction::West => Vector2D::new(-1, 0),
+        }
+    }
+
+    fn state<'a>(
+        &self,
+        h: &'a mut HashMap<Direction, bool>,
+        v: &'a mut HashMap<Direction, bool>,
+    ) -> &'a mut HashMap<Direction, bool> {
+        match self {
+            Direction::North | Direction::South => v,
+            Direction::East | Direction::West => h,
+        }
+    }
+}
+
 #[derive(Debug, Clone, Copy, PartialEq, Eq)]
 enum Tile {
     Vertical,
@@ -18,28 +52,28 @@ enum Tile {
 }
 
 impl Tile {
-    fn connections(&self) -> Vec<Vector2D<isize>> {
+    fn directions(&self) -> Vec<Direction> {
         match self {
-            Tile::Vertical => vec![Vector2D::new(0, -1), Vector2D::new(0, 1)],
-            Tile::Horizontal => vec![Vector2D::new(-1, 0), Vector2D::new(1, 0)],
-            Tile::NorthEast => vec![Vector2D::new(0, -1), Vector2D::new(1, 0)],
-            Tile::NorthWest => vec![Vector2D::new(0, -1), Vector2D::new(-1, 0)],
-            Tile::SouthWest => vec![Vector2D::new(-1, 0), Vector2D::new(0, 1)],
-            Tile::SouthEast => vec![Vector2D::new(0, 1), Vector2D::new(1, 0)],
+            Tile::Vertical => vec![Direction::North, Direction::South],
+            Tile::Horizontal => vec![Direction::East, Direction::West],
+            Tile::NorthEast => vec![Direction::North, Direction::East],
+            Tile::NorthWest => vec![Direction::North, Direction::West],
+            Tile::SouthWest => vec![Direction::South, Direction::West],
+            Tile::SouthEast => vec![Direction::South, Direction::East],
             Tile::Ground => vec![],
             Tile::Start => vec![
-                Vector2D::new(0, -1),
-                Vector2D::new(0, 1),
-                Vector2D::new(-1, 0),
-                Vector2D::new(1, 0),
+                Direction::North,
+                Direction::East,
+                Direction::South,
+                Direction::West,
             ],
         }
     }
 
     fn next(&self, position: Vector2D<isize>) -> Vec<Vector2D<isize>> {
-        self.connections()
+        self.directions()
             .iter()
-            .map(|dv| *dv + position)
+            .map(|d| d.direction_vector() + position)
             .collect_vec()
     }
 }
@@ -174,41 +208,28 @@ impl Solution<Output1, Output2> for Day10 {
 
         let mut counter = 0;
 
-        let mut horizontally_enclosed_west = vec![false; self.pipes[0].len()];
-        let mut horizontally_enclosed_east = vec![false; self.pipes[0].len()];
+        let mut horizontal_enclosure: Vec<HashMap<Direction, bool>> =
+            vec![
+                HashMap::from([(Direction::West, false), (Direction::East, false)]);
+                self.pipes[0].len()
+            ];
 
         for (y, row) in self.pipes.iter().enumerate() {
-            let mut vertically_enclosed_north = false;
-            let mut vertically_enclosed_south = false;
+            let mut vertical_enclosure: HashMap<Direction, bool> =
+                HashMap::from([(Direction::North, false), (Direction::South, false)]);
+
             for (x, &t) in row.iter().enumerate() {
                 if self.distances[y][x] != -1 {
-                    if matches!(
-                        t,
-                        Tile::Vertical | Tile::NorthEast | Tile::NorthWest | Tile::Start
-                    ) {
-                        vertically_enclosed_north = !vertically_enclosed_north;
-                    }
-                    if matches!(
-                        t,
-                        Tile::Vertical | Tile::SouthEast | Tile::SouthWest | Tile::Start
-                    ) {
-                        vertically_enclosed_south = !vertically_enclosed_south;
-                    }
+                    for direction in t.directions() {
+                        let directed_state: &mut HashMap<Direction, bool> =
+                            direction.state(&mut horizontal_enclosure[x], &mut vertical_enclosure);
 
-                    if matches!(
-                        t,
-                        Tile::Horizontal | Tile::NorthWest | Tile::SouthWest | Tile::Start
-                    ) {
-                        horizontally_enclosed_west[x] = !horizontally_enclosed_west[x];
+                        if let Some(val) = directed_state.get_mut(&direction) {
+                            *val = !*val;
+                        }
                     }
-                    if matches!(
-                        t,
-                        Tile::Horizontal | Tile::NorthEast | Tile::SouthEast | Tile::Start
-                    ) {
-                        horizontally_enclosed_east[x] = !horizontally_enclosed_east[x];
-                    }
-                } else if (vertically_enclosed_north || vertically_enclosed_south)
-                    && (horizontally_enclosed_east[x] || horizontally_enclosed_west[x])
+                } else if vertical_enclosure.values().any(|x| *x)
+                    && horizontal_enclosure[x].values().any(|x| *x)
                 {
                     counter += 1;
                 }