amicable.rs

fn d(n: i32) -> i32 {
    (2..(n / 2 + 1)).
        filter(|m| n % m == 0).
        fold(1, |result, i| result + i)
}

fn amicable(n: i32) -> i32 {
    let dn = d(n);
    let ddn = d(dn);

    if ddn == n && n != dn && n < 100_000 {
        n
    } else {
        0
    }
}

fn main() {
    let mut result = 0;

    for i in 1 .. 10_000 {
        result += amicable(i);
    }

    println!("{}", result);
}