projecteuler.net/012/main.rs

use std::fs::File;
use std::io::{ self, BufRead, BufReader };


fn get_ps() -> Vec<u32> {
    let file = File::open("primes.txt").unwrap();
    let lines = io::BufReader::new(file).lines();
    return lines.map(|line| line.unwrap().parse::<u32>().unwrap())
                .collect();
}

fn div_num(ps: &Vec<u32>, n: u32) -> u32 {
    fn max_div(m: u32, k: u32) -> u32 {
        let mut res = 0;
        let mut mm = m;
        while mm % k == 0 {
            mm /= k;
            res += 1;
        }
        res
    }

    let mut res = 1;
    for p in ps {
        let md = max_div(n, *p) + 1;
        res *= md;
    }

    return res;
}

fn main() {
    let ps = get_ps();
    let mut n = 1;
    let mut best_dn = 1;
    for k in 2..80000 {
        n += k;
        let dn = div_num(&ps, n);
        if dn > best_dn {
            best_dn = dn;
            println!("[{}]{}:{}", k, n, dn);
        }
    }
}