Rust Day 2 Part 2

rust/Cargo.lock

@@ -4,4 +4,4 @@ version = 3
 
 [[package]]
 name = "advent-of-code"
-version = "23.2.1"
+version = "23.2.2"

rust/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "advent-of-code"
-version = "23.2.1"
+version = "23.2.2"
 edition = "2021"
 default-run = "day02"
 

rust/src/day02/part_2.rs

@@ -1,5 +1,86 @@
-pub(crate) fn part_2(_input: &'static str) -> u64 {
-    todo!("Part 2")
+#[derive(Default)]
+struct CubeCounts {
+    red: u16,
+    green: u16,
+    blue: u16,
+}
+impl CubeCounts {
+    const fn power(&self) -> u16 {
+        self.red * self.green * self.blue
+    }
+}
+
+impl std::ops::Add<CubeCounts> for CubeCounts {
+    type Output = Self;
+
+    fn add(self, rhs: CubeCounts) -> Self::Output {
+        Self {
+            red: self.red + rhs.red,
+            green: self.green + rhs.green,
+            blue: self.blue + rhs.blue,
+        }
+    }
+}
+
+impl std::iter::Sum<CubeCounts> for CubeCounts {
+    fn sum<I: Iterator<Item = CubeCounts>>(iter: I) -> Self {
+        iter.fold(CubeCounts::default(), |acc, x| acc + x)
+    }
+}
+
+pub(crate) fn part_2(input: &'static str) -> u16 {
+    let id_sum = input
+        .lines()
+        .map(|line| {
+            let game_start_index = line.find(":").expect("Every line should have a ': '") + 2;
+
+            let game = &line[game_start_index..];
+
+            let groups = game.split("; ");
+
+            let game_counts = groups
+                .map(|group| {
+                    let color_counts = group.split(", ");
+
+                    let group_counts =
+                        color_counts.map(|color_count| {
+                            let (count, color) = color_count
+                                .split_once(' ')
+                                .expect("Every color count should have one space");
+
+                            let count = count.parse().expect(
+                        format!("Every color count should be a valid number - `{count}` `{color}`")
+                            .as_str(),
+                    );
+
+                            match color {
+                                "red" => CubeCounts {
+                                    red: count,
+                                    ..Default::default()
+                                },
+                                "green" => CubeCounts {
+                                    green: count,
+                                    ..Default::default()
+                                },
+                                "blue" => CubeCounts {
+                                    blue: count,
+                                    ..Default::default()
+                                },
+                                _ => unreachable!(),
+                            }
+                        });
+                    group_counts.sum::<CubeCounts>()
+                })
+                .reduce(|acc, cube_count| CubeCounts {
+                    red: u16::max(acc.red, cube_count.red),
+                    green: u16::max(acc.green, cube_count.green),
+                    blue: u16::max(acc.blue, cube_count.blue),
+                })
+                .expect("At least one group should exist in each game");
+            game_counts.power()
+        })
+        .sum();
+    id_sum
 }
 
 #[cfg(test)]
@@ -8,17 +89,11 @@ mod tests {
 
     #[test]
     fn test_with_sample_solution() {
-        assert_eq!(
-            super::part_2(SAMPLE_INPUT),
-            todo!("Add result from example part 2")
-        );
+        assert_eq!(super::part_2(SAMPLE_INPUT), 2286);
     }
 
     #[test]
     fn test_with_solution() {
-        assert_eq!(
-            super::part_2(crate::INPUT),
-            todo!("Add result for solved part 2")
-        );
+        assert_eq!(super::part_2(crate::INPUT), 63981);
     }
 }