feat(03/2015): solve second part

Author: manhunto

readme.md

@@ -89,7 +89,7 @@
 |----------------------------------------------------------------------------------|:------:|-----------------:|-----------------:|
 | [Day 1: Not Quite Lisp](src/solutions/year2015/day01.rs)                         |   ⭐⭐   |            0.013 |            0.001 |
 | [Day 2: I Was Told There Would Be No Math](src/solutions/year2015/day02.rs)      |   ⭐⭐   |            0.074 |            0.105 |
-| [Day 3: Perfectly Spherical Houses in a Vacuum](src/solutions/year2015/day03.rs) |   ⭐    |            0.358 |                - |
+| [Day 3: Perfectly Spherical Houses in a Vacuum](src/solutions/year2015/day03.rs) |   ⭐⭐   |            0.358 |            0.373 |
 
 # TODO
 

src/solutions/year2015/day03.rs

@@ -2,34 +2,64 @@ use crate::solutions::Solution;
 use crate::utils::point::Point;
 use std::collections::HashMap;
 
+type Houses = HashMap<Point, u64>;
+
 pub struct Day03;
 
 impl Solution for Day03 {
     fn part_one(&self, input: &str) -> String {
-        let mut visited_houses: HashMap<Point, u64> = HashMap::new();
-        let mut current = Point::new(0, 0);
-
-        visited_houses.insert(current, 1);
+        let mut visited_houses: Houses = HashMap::new();
+        let mut santa = Point::new(0, 0);
+        visited_houses.insert(santa, 1);
 
         for b in input.bytes() {
-            current = match b {
-                b'>' => current.east(),
-                b'<' => current.west(),
-                b'^' => current.north(),
-                b'v' => current.south(),
-                _ => unreachable!(),
+            santa = self.make_move(santa, b);
+
+            self.visit_house(&mut visited_houses, santa);
+        }
+
+        visited_houses.len().to_string()
+    }
+
+    fn part_two(&self, input: &str) -> String {
+        let mut visited_houses: Houses = HashMap::new();
+        let mut santa = Point::new(0, 0);
+        visited_houses.insert(santa, 1);
+
+        let mut robo_santa = Point::new(0, 0);
+        visited_houses.insert(robo_santa, 1);
+
+        for (i, b) in input.bytes().enumerate() {
+            let visited = if i % 2 == 0 {
+                santa = self.make_move(santa, b);
+
+                santa
+            } else {
+                robo_santa = self.make_move(robo_santa, b);
+
+                robo_santa
             };
-            visited_houses
-                .entry(current)
-                .and_modify(|e| *e += 1)
-                .or_insert(1);
+
+            self.visit_house(&mut visited_houses, visited);
         }
 
-        visited_houses.keys().count().to_string()
+        visited_houses.len().to_string()
     }
+}
 
-    fn part_two(&self, _input: &str) -> String {
-        String::from("0")
+impl Day03 {
+    fn make_move(&self, point: Point, b: u8) -> Point {
+        match b {
+            b'>' => point.east(),
+            b'<' => point.west(),
+            b'^' => point.north(),
+            b'v' => point.south(),
+            _ => unreachable!(),
+        }
+    }
+
+    fn visit_house(&self, houses: &mut Houses, house: Point) {
+        houses.entry(house).and_modify(|e| *e += 1).or_insert(1);
     }
 }
 
@@ -43,4 +73,11 @@ mod tests {
         assert_eq!("4", Day03.part_one("^>v<"));
         assert_eq!("2", Day03.part_one("^v^v^v^v^v"));
     }
+
+    #[test]
+    fn part_two_example_test() {
+        assert_eq!("3", Day03.part_two("^v"));
+        assert_eq!("3", Day03.part_two("^>v<"));
+        assert_eq!("11", Day03.part_two("^v^v^v^v^v"));
+    }
 }