projecteuler.net/047/main.rs

use std::collections::HashSet;

type HS = HashSet<u32>;

fn er() -> HS {
    let mut nums = Vec::new();
    let size = 1_000;
    for n in 0..size+1 { nums.push(true); }
    let mut p = 1;
    loop {
        let mut found = false;
        for i in p+1..size {
            if nums[i] {
                found = true;
                p = i;
                break;
            }
        }
        if !found { break; }
        for i in (2 * p .. size).step_by(p) {
            nums[i] = false;
        }
    }
    let mut res = HashSet::new();
    for i in 2..size {
        if nums[i] { res.insert(i as u32); }
    }
    return res;
}

fn cj(n: u32, ps: &HS) -> u64 {
    let mut nn = n;
    let mut pc = 0;

        for p in ps.iter() {
            if nn == 1 {
                break;
            }
            if nn % p == 0 {
                pc += 1;
                while nn % p == 0 {
                    nn /= p;
                }
            }
        }
    
    return pc;
}

fn main() {
    let ps = er();
    for n in 2..10_00000 {
        let mut found = true;
        for k in 0..=3 {
            let t = cj(n + k, &ps);
            if t != 4 {
                found = false;
                break;
            }
        }
        if found {
            println!("{}", n);
            break;
        }
    }
}