Advent-of-Code/2023/day-01/src/part2.rs

use color_eyre::Result;

pub fn process(input: &str) -> Result<u32> {
    let sum: u32 = input.lines().map(process_line).sum();

    Ok(sum)
}

fn process_line(line: &str) -> u32 {
    let mut it = (0..line.len()).filter_map(|index| {
        let reduced_line = &line[index..];
        let result = if reduced_line.starts_with("one") {
            Some(1)
        } else if reduced_line.starts_with("two") {
            Some(2)
        } else if reduced_line.starts_with("three") {
            Some(3)
        } else if reduced_line.starts_with("four") {
            Some(4)
        } else if reduced_line.starts_with("five") {
            Some(5)
        } else if reduced_line.starts_with("six") {
            Some(6)
        } else if reduced_line.starts_with("seven") {
            Some(7)
        } else if reduced_line.starts_with("eight") {
            Some(8)
        } else if reduced_line.starts_with("nine") {
            Some(9)
        } else {
            reduced_line.chars().next().unwrap().to_digit(10)
        };
        result
    });

    let first = it.next().expect("Should be a number");

    match it.last() {
        Some(num) => first * 10 + num,
        None => first * 10 + first,
    }
}

#[cfg(test)]
mod tests {
    use super::*;
    #[test]
    fn test_process() -> Result<()> {
        let input = "two1nine
eightwothree
abcone2threexyz
xtwone3four
4nineeightseven2
zoneight234
7pqrstsixteen";
        assert_eq!(281, process(input)?);
        Ok(())
    }
}