solution: day 6

data/examples/06.txt

@@ -0,0 +1,2 @@
+Time:      7  15   30
+Distance:  9  40  200

src/bin/06.rs

@@ -0,0 +1,63 @@
+use aoc::parsers::to_vec;
+
+fn win_options((time, distance): (u64, u64)) -> u64 {
+    let discriminant = ((time.pow(2) - 4 * distance) as f64).sqrt();
+
+    let first_zero = (time as f64 - discriminant) / 2.0;
+    let mut second_zero = (time as f64 + discriminant) / 2.0;
+
+    if second_zero.fract() == 0.0 {
+        second_zero -= 1.0
+    }
+
+    second_zero as u64 - first_zero as u64
+}
+
+pub fn part_one(input: &str) -> Option<u64> {
+    let (upt, upd) = input.split_once('\n')?;
+    let time: Vec<u64> = to_vec(upt.strip_prefix("Time:      ")?, ' ');
+    let distance: Vec<u64> = to_vec(upd.strip_prefix("Distance:  ")?, ' ');
+
+    Some(time.into_iter().zip(distance).map(win_options).product())
+}
+
+pub fn part_two(input: &str) -> Option<u64> {
+    let (upt, upd) = input.split_once('\n')?;
+    let time: u64 = upt
+        .strip_prefix("Time:      ")?
+        .split(' ')
+        .flat_map(|x| x.chars())
+        .collect::<String>()
+        .parse()
+        .ok()?;
+    let distance: u64 = upd
+        .strip_prefix("Distance:  ")?
+        .split(' ')
+        .flat_map(|x| x.chars())
+        .collect::<String>()
+        .parse()
+        .ok()?;
+
+    Some(win_options((time, distance)))
+}
+
+aoc::solution!(6);
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    #[test]
+    fn test_part_one() {
+        assert_eq!(
+            part_one(&aoc::template::read_file("examples", 6)),
+            Some(288)
+        );
+    }
+    #[test]
+    fn test_part_two() {
+        assert_eq!(
+            part_two(&aoc::template::read_file("examples", 6)),
+            Some(71503)
+        );
+    }
+}