feat(day02): working solution

src/day02.rs

@@ -0,0 +1,157 @@
+use crate::Day;
+
+// Register this day in our runner inventory
+inventory::submit! {
+    Day { number: 2, run }
+}
+
+#[derive(Debug, Default)]
+struct ColorCount {
+    id: usize,
+    red: usize,
+    green: usize,
+    blue: usize,
+}
+
+impl ColorCount {
+    fn max_by_element(&self, b: &Self) -> Self {
+        Self {
+            id: self.id,
+            red: self.red.max(b.red),
+            green: self.green.max(b.green),
+            blue: self.blue.max(b.blue),
+        }
+    }
+
+    fn is_possible(&self, max: &Self) -> bool {
+        self.red <= max.red && self.green <= max.green && self.blue <= max.blue
+    }
+
+    fn power(&self) -> usize {
+        self.red * self.green * self.blue
+    }
+}
+
+// takes a group like "1 blue, 2 green, 3 red" and returns a ColorCount object
+fn parse_group(group: &str) -> ColorCount {
+    let mut color_count = ColorCount::default();
+
+    // split group in to its individual colors
+    for part in group.split(", ") {
+        // split individual color into "number color"
+        let mut parts = part.split_whitespace();
+        let number = parts.next().unwrap().parse::<usize>().unwrap();
+        let color = parts.next().unwrap();
+
+        match color {
+            "red" => color_count.red += number,
+            "green" => color_count.green += number,
+            "blue" => color_count.blue += number,
+            _ => unreachable!(), // This should not happen if all colors are known.
+        }
+    }
+
+    color_count
+}
+
+fn parse_game(game_text: &str) -> ColorCount {
+    // Split apart the "Game X:" and color groups
+    let mut parts = game_text.splitn(2, ": ");
+
+    // Extract the game number from the first part.
+    let game_number = parts
+        .next()
+        .unwrap()
+        .split_whitespace()
+        .last()
+        .unwrap()
+        .parse::<usize>()
+        .unwrap();
+
+    // Get the color data from the second part.
+    let color_data = parts.next().unwrap();
+
+    // Create initial ColorCount object with the game number
+    let initial = ColorCount {
+        id: game_number,
+        ..Default::default()
+    };
+
+    // Parse the color groups and collect the maximum values found for each color
+    color_data
+        .split("; ")
+        .map(parse_group)
+        .fold(initial, |acc, x| acc.max_by_element(&x))
+}
+
+fn parse_games(games_text: &str) -> impl Iterator<Item = ColorCount> + '_ {
+    games_text
+        .lines()
+        .filter(|line| !line.is_empty())
+        .map(parse_game)
+}
+
+fn part1(input: &str) -> usize {
+    let max_color_count = ColorCount {
+        id: 0,
+        red: 12,
+        green: 13,
+        blue: 14,
+    };
+
+    // Find all the games which are <= max_color_count and sum the game ids
+    parse_games(input)
+        .filter(|x| x.is_possible(&max_color_count))
+        .map(|x| x.id)
+        .sum()
+}
+
+fn part2(input: &str) -> usize {
+    // Sum the (red*green*blue) for all games' maximum color counts
+    parse_games(input).map(|x| x.power()).sum()
+}
+
+const INPUT: &str = include_str!("../data/day02.dat");
+
+fn run() {
+    println!("{}", part1(INPUT));
+    println!("{}", part2(INPUT));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_part1_example() {
+        let input = r#"
+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
+"#;
+        assert_eq!(part1(input), 8);
+    }
+
+    #[test]
+    fn test_part1_actual() {
+        assert_eq!(part1(INPUT), 2683);
+    }
+
+    #[test]
+    fn test_part2_example() {
+        let input = r#"
+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
+"#;
+        assert_eq!(part2(input), 2286);
+    }
+    #[test]
+    fn test_part2_actual() {
+        assert_eq!(part2(INPUT), 49710);
+    }
+}