year2025/
day01.rs

1use utils::prelude::*;
2
3/// Counting how many times a dial passes zero.
4#[derive(Clone, Debug)]
5pub struct Day01 {
6    part1: u32,
7    part2: u32,
8}
9
10parser::parsable_enum! {
11    #[derive(Clone, Copy, Debug)]
12    enum Direction {
13        "L" => Left = -1,
14        "R" => Right = 1,
15    }
16}
17
18impl Day01 {
19    pub fn new(input: &str, _: InputType) -> Result<Self, InputError> {
20        let mut pos = 50i32;
21        let (mut part1, mut part2) = (0, 0);
22        for line in Direction::PARSER
23            .then(parser::number_range(1i32..=999))
24            .with_eol()
25            .parse_iterator(input)
26        {
27            let (dir, steps) = line?;
28
29            part2 += match dir {
30                Direction::Left => ((100 - pos + steps) / 100) as u32 - u32::from(pos == 0),
31                Direction::Right => ((pos + steps) / 100) as u32,
32            };
33
34            pos = (pos + (steps * dir as i32)).rem_euclid(100);
35            part1 += u32::from(pos == 0);
36        }
37
38        Ok(Self { part1, part2 })
39    }
40
41    #[must_use]
42    pub fn part1(&self) -> u32 {
43        self.part1
44    }
45
46    #[must_use]
47    pub fn part2(&self) -> u32 {
48        self.part2
49    }
50}
51
52examples!(Day01 -> (u32, u32) [
53    {input: "L68\nL30\nR48\nL5\nR60\nL55\nL1\nL99\nR14\nL82", part1: 3, part2: 6},
54]);
year2025/day01.rs

year2025/
day01.rs
