Year 2023, Day 06

year2023/src/day06.rs

@@ -0,0 +1,82 @@
+use common::day::Day;
+
+pub struct Day06 {}
+
+impl Day for Day06 {
+    fn star1(&self, input: &str) -> String {
+        let races = parse_part1(input);
+        races
+            .into_iter()
+            .map(|race| race.ways_to_win())
+            .product::<usize>()
+            .to_string()
+    }
+
+    fn star2(&self, input: &str) -> String {
+        let race = parse_part2(input);
+        race.ways_to_win().to_string()
+    }
+}
+
+struct Race {
+    time: usize,
+    distance: usize,
+}
+
+fn parse_part1(input: &str) -> Vec<Race> {
+    let lines: Vec<_> = input.lines().collect();
+    let times: Vec<_> = lines[0]
+        .split_whitespace()
+        .skip(1)
+        .map(|n| n.parse().unwrap())
+        .collect();
+    let distances: Vec<_> = lines[1]
+        .split_whitespace()
+        .skip(1)
+        .map(|n| n.parse().unwrap())
+        .collect();
+
+    times
+        .into_iter()
+        .zip(distances)
+        .map(|(time, distance)| Race { time, distance })
+        .collect()
+}
+
+fn parse_part2(input: &str) -> Race {
+    let lines: Vec<_> = input.lines().collect();
+    let time: String = lines[0].split_whitespace().skip(1).collect();
+    let distance: String = lines[1].split_whitespace().skip(1).collect();
+    Race {
+        time: time.parse().unwrap(),
+        distance: distance.parse().unwrap(),
+    }
+}
+
+impl Race {
+    fn ways_to_win(&self) -> usize {
+        (1..self.time)
+            .filter(|n| (self.time - n) * n > self.distance)
+            .count()
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const INPUT: &str = r#"Time:      7  15   30
+Distance:  9  40  200"#;
+
+    #[test]
+    fn star1() {
+        let d = Day06 {};
+        assert_eq!(d.star1(INPUT), "288");
+    }
+
+    #[test]
+    fn star2() {
+        let d = Day06 {};
+        assert_eq!(d.star2(INPUT), "71503");
+    }
+}

year2023/src/lib.rs

@@ -6,6 +6,7 @@ mod day02;
 mod day03;
 mod day04;
 mod day05;
+mod day06;
 
 pub struct Year2023 {}
 
@@ -17,6 +18,7 @@ impl Year for Year2023 {
             3 => Some(Box::new(day03::Day03 {})),
             4 => Some(Box::new(day04::Day04 {})),
             5 => Some(Box::new(day05::Day05 {})),
+            6 => Some(Box::new(day06::Day06 {})),
             _ => None,
         }
     }