day-6 done

2023/day-6/src/lib.rs

@@ -0,0 +1,4 @@
+pub mod part1;
+pub use crate::part1::*;
+pub mod part2;
+pub use crate::part2::*;

2023/day-6/src/main.rs

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+#![warn(clippy::all, clippy::pedantic)]
+
+use day_6::part1;
+use day_6::part2;
+
+fn main() {
+    let input = include_str!("./input.txt");
+    let part1_result = part1(input);
+    println!("part 1: {part1_result}");
+    let part2_result = part2(input);
+    println!("part 2: {part2_result}");
+}

2023/day-6/src/part1.rs

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+#![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 part1(input: &str) -> String {
+    let (_, races) = parse_input(input).expect("input expected");
+    races
+        .iter()
+        .map(|(time, distance)| {
+            (0..=*time)
+                .filter_map(|x| {
+                    if (time - x) * x > *distance {
+                        Some(())
+                    } else {
+                        None
+                    }
+                })
+                .count()
+        })
+        .product::<usize>()
+        .to_string()
+}
+
+fn parse_input(input: &str) -> IResult<&str, Vec<(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)?;
+
+    Ok((
+        input,
+        time.iter()
+            .interleave(distance.iter())
+            .map(|x| *x)
+            .tuples()
+            .collect(),
+    ))
+}
+
+#[cfg(test)]
+mod test {
+    use super::*;
+
+    const INPUT: &str = "Time:      7  15   30
+Distance:  9  40  200";
+
+    #[test]
+    fn part1_works() {
+        let result = part1(INPUT);
+        assert_eq!(result, "288".to_string());
+    }
+}

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());
+    }
+}