Day 6 - Part 1

Signed-off-by: Anthony Oteri <anthony.oteri@gmail.com>

day-06/Cargo.toml

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+[package]
+name = "day-06"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+itertools = "0.12.0"
+nom = "7.1.3"
+nom-supreme = "0.8.0"
+tracing = "0.1.40"
+tracing-subscriber = "0.3.18"
+
+[dev-dependencies]
+env_logger = "0.10.1"
+test-log = "0.2.13"

day-06/input.txt

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+Time:        35     69     68     87
+Distance:   213   1168   1086   1248

day-06/src/main.rs

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+use nom::{
+    bytes::complete::is_not,
+    character::complete::{self, line_ending, space1},
+    multi::separated_list1,
+    sequence::separated_pair,
+    IResult, Parser as _,
+};
+use nom_supreme::ParserExt as _;
+use tracing::instrument;
+
+#[derive(Debug, Clone, Eq, PartialEq)]
+struct Race {
+    time: u64,
+    record: u64,
+}
+
+impl Race {
+    fn distance(&self) -> Vec<u64> {
+        (0..self.time)
+            .map(|t| t * (self.time - t))
+            .collect::<Vec<u64>>()
+    }
+}
+
+fn nums(input: &str) -> IResult<&str, Vec<u64>> {
+    is_not("0123456789")
+        .precedes(separated_list1(space1, complete::u64))
+        .parse(input)
+}
+
+fn parse_times(input: &str) -> IResult<&str, Vec<Race>> {
+    let (input, (times, records)) = separated_pair(nums, line_ending, nums).parse(input)?;
+
+    let races = itertools::izip!(&times, &records)
+        .map(|(&time, &record)| Race { time, record })
+        .collect();
+
+    Ok((input, races))
+}
+
+#[instrument]
+fn part_1(input: &str) -> usize {
+    let (_, races) = parse_times(input).unwrap();
+
+    let results = races
+        .iter()
+        .map(|r| {
+            r.distance()
+                .into_iter()
+                .filter(|&d| d > r.record)
+                .collect::<Vec<u64>>()
+        })
+        .collect::<Vec<Vec<u64>>>();
+
+    results.iter().map(Vec::len).product()
+}
+
+fn main() {
+    let input = include_str!("../input.txt");
+    println!("Part 1: {}", part_1(input));
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test_log::test]
+    fn test_part_1() {
+        tracing::info!("Hello world");
+        let input = include_str!("../test-input.txt");
+        assert_eq!(part_1(input), 288);
+    }
+}

day-06/test-input.txt

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+Time:      7  15   30
+Distance:  9  40  200