#[test]
fn return_3() {
    assert_eq!(3, captcha("1122"))
}

#[test]
fn return_4() {
    assert_eq!(4, captcha("1111"))
}

#[test]
fn return_0() {
    assert_eq!(0, captcha("1234"))
}

fn captcha(number_string: &str) -> u32 {
    let mut out : u32 = 0;
    let mut number_chars = number_string.chars().peekable();
    let first = number_chars.nth(0);
    let mut this_char = first;
    loop {
        match this_char {
            Some(i) => {
                match number_chars.peek() {
                    Some(j) => {
                        if i == *j {
                            out += i.to_digit(10).unwrap();
                        }
                    },
                    None => {
                        if i == first.unwrap() {
                            out += i.to_digit(10).unwrap();
                        }
                        break;
                    }
                };
            },
            None => ()
        };
        this_char = number_chars.next();
    }
    out
}