Advent of Code 2017 - Day 1 (in Rust)

main.rs

fn inverse_captcha(input: &str) -> u32 {
    if input.len() <= 1 {
        return 0u32;
    }

    let mut prev = 0;
    let mut total: u32 = 0;
    let mut numbers: Vec<u32> = input.chars().map(|c| c.to_digit(10).unwrap()).collect();
    let firstNumber = numbers[0];

    numbers.push(firstNumber);

    for num in numbers.iter() {
        if prev == *num {
            total += *num;
        }
        prev = *num;
    }

    total
}

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

    #[test]
    fn check_inverse_captcha_1122() {
        assert!(inverse_captcha("1122") == 3);
    }

    #[test]
    fn check_inverse_captcha_1111() {
        assert!(inverse_captcha("1111") == 4);
    }

    #[test]
    fn check_inverse_captcha_1234() {
        assert!(inverse_captcha("1234") == 0);
    }

    #[test]
    fn check_inverse_captcha_91212129() {
        assert!(inverse_captcha("91212129") == 9);
    }
}