keck.rs

extern crate md5;

fn find_number<F: Fn(md5::Digest) -> bool>(key: &str, predicate: F) -> u32 {
    for n in 0.. {
        let s = format!("{}{}", key, n);
        let digest = md5::compute(s.as_bytes());
        if predicate(digest) {
            return n;
        }
    }
    unreachable!()
}

fn first_5_zeroes(digest: md5::Digest) -> bool {
    digest[0] == 0 && digest[1] == 0 && digest[2] <= 0xF
}

fn first_6_zeroes(digest: md5::Digest) -> bool {
    digest[0] == 0 && digest[1] == 0 && digest[2] == 0
}

#[test]
fn test_find_number() {
    assert_eq!(find_number("abcdef", first_5_zeroes), 609043);
    assert_eq!(find_number("pqrstuv", first_5_zeroes), 1048970);
}

fn main() {
    const SECRET_KEY: &'static str = "ckczppom";
    println!("The number is {}", find_number(SECRET_KEY, first_5_zeroes));
    println!("For first 6 zeroes: {}",
             find_number(SECRET_KEY, first_6_zeroes));
}