82 lines
2.1 KiB
Rust
82 lines
2.1 KiB
Rust
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use nom::{
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branch::alt,
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bytes::complete::tag,
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character::complete::{char, digit1},
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combinator::{map, value},
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multi::separated_list1,
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sequence::{delimited, pair, terminated, tuple},
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IResult,
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};
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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) -> u32 {
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input.lines().map(game).sum()
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}
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fn game(input: &str) -> u32 {
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let (_, product) = tuple((id, all_results))(input).unwrap().1;
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product
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}
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fn digit_u32(i: &str) -> IResult<&str, u32> {
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map(digit1, |d: &str| d.parse().unwrap())(i)
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}
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fn id(i: &str) -> IResult<&str, u32> {
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delimited(tag("Game "), digit_u32, tag(": "))(i)
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}
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fn all_results(i: &str) -> IResult<&str, u32> {
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map(separated_list1(tag("; "), one_result), |res| {
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let (red, green, blue) =
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res.iter()
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.flatten()
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.fold(
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(0_u32, 0_u32, 0_u32),
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|(r, g, b), (amount, color)| match color {
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Color::Red => (r.max(*amount), g, b),
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Color::Green => (r, g.max(*amount), b),
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Color::Blue => (r, g, b.max(*amount)),
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},
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);
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red * green * blue
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})(i)
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}
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fn one_result(i: &str) -> IResult<&str, Vec<(u32, Color)>> {
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separated_list1(tag(", "), color)(i)
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}
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#[derive(Debug, PartialEq, Clone, Copy)]
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enum Color {
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Red,
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Green,
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Blue,
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}
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fn color(i: &str) -> IResult<&str, (u32, Color)> {
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pair(
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terminated(digit_u32, char(' ')),
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alt((
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value(Color::Red, tag("red")),
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value(Color::Green, tag("green")),
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value(Color::Blue, tag("blue")),
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)),
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)(i)
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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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#[test]
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fn test_part2() {
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assert_eq!(part2("Game 1: 3 blue, 4 red; 1 red, 2 green, 6 blue; 2 green\nGame 2: 1 blue, 2 green; 3 green, 4 blue, 1 red; 1 green, 1 blue\nGame 3: 8 green, 6 blue, 20 red; 5 blue, 4 red, 13 green; 5 green, 1 red\nGame 4: 1 green, 3 red, 6 blue; 3 green, 6 red; 3 green, 15 blue, 14 red\nGame 5: 6 red, 1 blue, 3 green; 2 blue, 1 red, 2 green"), 2286)
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}
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}
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