Solution for Advent of Code 2017 Day 1

day01.rs

use std::time::Instant;

const INPUT: &str = include_str!("inputs/day01.txt");

fn parse(input: &str) -> impl Iterator<Item = u32> {
    input.trim().chars().map(|c| c.to_digit(10).unwrap())
}

fn p1(input: &str) -> u32 {
    let input = parse(input).collect::<Vec<_>>();
    input
        .iter()
        .zip(input.iter().cycle().skip(1))
        .filter(|(l, r)| l == r)
        .map(|(l, _)| l)
        .sum()
}

fn p2(input: &str) -> u32 {
    let input = parse(input).collect::<Vec<_>>();
    input
        .iter()
        .zip(input.iter().cycle().skip(input.len() / 2))
        .filter(|(l, r)| l == r)
        .map(|(l, _)| l)
        .sum()
}

fn main() {
    let now = Instant::now();
    let solution = p1(INPUT);
    println!("p1 {:?} {}", now.elapsed(), solution);

    let now = Instant::now();
    let solution = p2(INPUT);
    println!("p2 {:?} {}", now.elapsed(), solution);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test_p1() {
        let input = "1111";
        assert_eq!(p1(input), 4);
    }

    #[test]
    fn test_p2() {
        let input = "12131415";
        assert_eq!(p2(input), 4);
    }
}