66 lines
1.5 KiB
Rust
66 lines
1.5 KiB
Rust
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use nom::{
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bytes::complete::tag,
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character::complete::{digit1, newline, space1},
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multi::separated_list1,
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sequence::{pair, preceded, separated_pair},
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IResult, Parser,
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};
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use rayon::prelude::*;
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fn main() {
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println!("{}", part2(include_str!("./input.txt")));
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}
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fn part2(input: &str) -> u64 {
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separated_pair(time_parser, newline, distance_parser)
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.map(|(time, distance)| calc_game(time, distance))
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.parse(input)
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.unwrap()
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.1
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}
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fn time_parser(i: &str) -> IResult<&str, u64> {
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preceded(pair(tag("Time:"), space1), separated_list1(space1, digit1))
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.map(|strs| strs.join("").parse::<u64>().expect("Invalid digit"))
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.parse(i)
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}
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fn distance_parser(i: &str) -> IResult<&str, u64> {
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preceded(
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pair(tag("Distance:"), space1),
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separated_list1(space1, digit1),
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)
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.map(|strs| strs.join("").parse::<u64>().expect("Invalid digit"))
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.parse(i)
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}
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fn calc_game(time: u64, distance: u64) -> u64 {
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(1..time)
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.into_par_iter()
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.filter_map(|t| (calc_distance(t, time) > distance).then_some(()))
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.count() as u64
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}
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fn calc_distance(hold_time: u64, total_time: u64) -> u64 {
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hold_time * (total_time - hold_time)
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}
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#[cfg(test)]
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mod tests {
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use super::*;
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use indoc::indoc;
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#[test]
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fn test_part1() {
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assert_eq!(
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part2(indoc!(
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"
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Time: 7 15 30
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Distance: 9 40 200
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"
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)),
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288
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);
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}
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}
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