solution: day 2

data/examples/02.txt

@@ -0,0 +1,6 @@
+Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green
+Game 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue
+Game 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red
+Game 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red
+Game 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green
+

src/bin/02.rs

@@ -0,0 +1,100 @@
+use std::str::FromStr;
+
+use aoc::parsers::to_vec;
+
+struct Game {
+    id: u32,
+    balls: Vec<(u32, String)>,
+}
+
+impl FromStr for Game {
+    type Err = String;
+    fn from_str(s: &str) -> Result<Self, Self::Err> {
+        let rest = s.strip_prefix("Game ").unwrap();
+        let (id, rest) = rest.split_once(':').unwrap();
+        let id = id.parse().unwrap();
+
+        let balls = rest
+            .split([',', ';'])
+            .map(|x| x.strip_prefix(' ').unwrap().split_once(' ').unwrap())
+            .map(|(n, c)| (n.parse::<u32>().unwrap(), c.to_string()))
+            .collect();
+
+        Ok(Game { id, balls })
+    }
+}
+
+pub fn part_one(input: &str) -> Option<u32> {
+    let games: Vec<Game> = to_vec(input, '\n');
+
+    let mut id_sum = 0;
+
+    'games: for g in games {
+        for (n, c) in g.balls {
+            match c.as_str() {
+                "blue" => {
+                    if n > 14 {
+                        continue 'games;
+                    }
+                }
+                "red" => {
+                    if n > 12 {
+                        continue 'games;
+                    }
+                }
+                "green" => {
+                    if n > 13 {
+                        continue 'games;
+                    }
+                }
+                _ => continue 'games,
+            }
+        }
+
+        id_sum += g.id;
+    }
+
+    Some(id_sum)
+}
+
+pub fn part_two(input: &str) -> Option<u32> {
+    let games: Vec<Game> = to_vec(input, '\n');
+
+    let mut total_power = 0;
+
+    for g in games {
+        let power: u32 = ["blue", "red", "green"]
+            .iter()
+            .map(|&c| {
+                g.balls
+                    .iter()
+                    .filter(|(_, cd)| c == cd.as_str())
+                    .map(|(n, _)| n)
+                    .max()
+                    .unwrap()
+            })
+            .product();
+
+        total_power += power;
+    }
+
+    Some(total_power)
+}
+
+aoc::solution!(2);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        assert_eq!(part_one(&aoc::template::read_file("examples", 2)), Some(8));
+    }
+    #[test]
+    fn test_part_two() {
+        assert_eq!(
+            part_two(&aoc::template::read_file("examples", 2)),
+            Some(2286)
+        );
+    }
+}