day4.rs

fn main() {
    let range = 235741..=706948;
    let n_matches = range.into_iter().filter(|n| match_criteria(*n)).count();
    println!("Number of matches: {}", n_matches)
}

fn match_criteria(candidate: i32) -> bool {
    let n1 = candidate % 10;
    let n2 = (candidate / 10) % 10;
    let n3 = (candidate / 100) % 10;
    let n4 = (candidate / 1000) % 10;
    let n5 = (candidate / 10000) % 10;
    let n6 = (candidate / 100000) % 10;
    let p = vec!(n6, n5, n4, n3, n2, n1);
    let mut double = false;
    for i in 1..6 {
        if p[i] < p[i-1] {
            return false
        }
        let d_cand = (p[i] == p[i-1]) && !((i > 1 && p[i-2] == p[i-1]) || (i < 5 && p[i] == p[i+1]));
        double = double || d_cand
    }
    double
}