day-6 done

2023/day-6/src/part2.rs

@@ -0,0 +1,65 @@
+#![warn(clippy::all, clippy::pedantic)]
+
+use itertools::Itertools;
+use nom::{
+    bytes::complete::tag,
+    character::complete,
+    multi::separated_list1,
+    sequence::{pair, preceded},
+    IResult,
+};
+
+#[must_use]
+pub fn part2(input: &str) -> String {
+    let (_, race) = parse_input(input).expect("input expected");
+    (0..=race.0)
+        .filter_map(|x| {
+            if (race.0 - x) * x > race.1 {
+                Some(())
+            } else {
+                None
+            }
+        })
+        .count()
+        .to_string()
+}
+
+fn parse_input(input: &str) -> IResult<&str, (u64, u64)> {
+    let (input, time) = preceded(
+        pair(tag("Time:"), complete::space1),
+        separated_list1(complete::space1, complete::u64),
+    )(input)?;
+    let (input, _) = complete::line_ending(input)?;
+    let (input, distance) = preceded(
+        pair(tag("Distance:"), complete::space1),
+        separated_list1(complete::space1, complete::u64),
+    )(input)?;
+    let distance = distance
+        .iter()
+        .map(|x| x.to_string())
+        .join("")
+        .parse::<u64>()
+        .expect("is a number");
+    let time = time
+        .iter()
+        .map(|x| x.to_string())
+        .join("")
+        .parse::<u64>()
+        .expect("is a number");
+
+    Ok((input, (time, distance)))
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const INPUT: &str = "Time:      7  15   30
+Distance:  9  40  200";
+
+    #[test]
+    fn part2_works() {
+        let result = part2(INPUT);
+        assert_eq!(result, "71503".to_string());
+    }
+}