day06 solution

2023/src/day06.rs

@@ -0,0 +1,93 @@
+use aoc_runner_derive::{aoc, aoc_generator};
+
+#[derive(Debug)]
+struct Race {
+    time: u64,
+    distance: u64,
+}
+
+impl Race {
+    fn winning_times(&self) -> Vec<u64> {
+        let mut result: Vec<u64> = vec![];
+        for t in 0..=self.time {
+            if t * (self.time - t) > self.distance {
+                result.push(t);
+            }
+        }
+        result
+    }
+}
+
+#[aoc_generator(day6)]
+fn parse(input: &str) -> Vec<Race> {
+    let mut lines = input.lines();
+    let times: Vec<u64> = lines.next().unwrap().split(": ").collect::<Vec<&str>>()[1]
+        .trim_start()
+        .split(" ")
+        .filter_map(|t| t.parse::<u64>().ok())
+        .collect();
+    let distances: Vec<u64> = lines.next().unwrap().split(": ").collect::<Vec<&str>>()[1]
+        .trim_start()
+        .split(" ")
+        .filter_map(|t| t.parse::<u64>().ok())
+        .collect();
+    assert_eq!(times.len(), distances.len());
+    (0..times.len())
+        .map(|i| Race {
+            time: times[i],
+            distance: distances[i],
+        })
+        .collect()
+}
+
+#[aoc(day6, part1)]
+fn part1(input: &[Race]) -> u64 {
+    input
+        .iter()
+        .map(|race| race.winning_times().len() as u64)
+        .collect::<Vec<u64>>()
+        .iter()
+        .product()
+}
+
+#[aoc(day6, part2)]
+fn part2(input: &[Race]) -> u64 {
+    let time = input
+        .iter()
+        .map(|race| race.time)
+        .collect::<Vec<u64>>()
+        .iter()
+        .map(|t| t.to_string())
+        .collect::<Vec<String>>()
+        .join("")
+        .parse::<u64>()
+        .unwrap();
+    let distance = input
+        .iter()
+        .map(|race| race.distance)
+        .collect::<Vec<u64>>()
+        .iter()
+        .map(|t| t.to_string())
+        .collect::<Vec<String>>()
+        .join("")
+        .parse::<u64>()
+        .unwrap();
+    let race = Race { time, distance };
+    race.winning_times().len() as u64
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    const SAMPLE_DATA: &'static str = r#"Time:      7  15   30
+Distance:  9  40  200
+"#;
+
+    #[test]
+    fn sample_data() {
+        let races = parse(&SAMPLE_DATA);
+        assert_eq!(part1(&races), 288);
+        assert_eq!(part2(&races), 71503);
+    }
+}

2023/src/lib.rs

@@ -5,5 +5,6 @@ mod day02;
 mod day03;
 mod day04;
 mod day05;
+mod day06;
 
 aoc_lib! { year = 2023 }