main.rs

pub fn main() {
    println!(
        "{}",
        include_bytes!("../input.txt")
            .split(|&b| b == b'\n')
            .map(|line| {
                let mut part = line.splitn(2, |&b| b == b'|');
                let mut input = part.next().unwrap().split(|&b| b == b' ');
                let one = input.clone().find(|d| d.len() == 2).unwrap();
                let four = input.find(|d| d.len() == 4).unwrap();
                part.next()
                    .unwrap()
                    .split(|&b| b == b' ')
                    .skip(1)
                    .map(|d| match d.len() {
                        2 => 1,
                        3 => 7,
                        4 => 4,
                        7 => 8,
                        len => match (
                            len,
                            d.iter().filter(|&b| one.contains(b)).count(),
                            d.iter().filter(|&b| four.contains(b)).count(),
                        ) {
                            (5, 1, 3) => 5,
                            (5, 2, 3) => 3,
                            (5, _, 2) => 2,
                            (6, 1, _) => 6,
                            (6, _, 3) => 0,
                            (6, _, 4) => 9,
                            _ => unreachable!(),
                        },
                    })
                    .enumerate()
                    .fold(0, |acc, (i, n)| acc + n * 10_u32.pow(3 - i as u32))
            })
            .sum::<u32>()
    );
}