projecteuler.net/035/main.rs

use std::collections::HashSet;

fn er() -> HashSet<u32> {
    let mut nums = Vec::new();
    let size = 1_000_000;
    for n in 0..size+1 { nums.push(true); }
    let mut p = 1;
    while true {
        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 rt(n: u32) -> u32 {
    let s = n.to_string();
    let mut chars = s.chars();
    let f = chars.next().unwrap();
    //chars.next_back();
    let mut res = String::from(chars.as_str());
    res.push(f);
    res.parse::<u32>().unwrap()
}

fn rts(n: u32) -> Vec<u32> {
    let mut k = n;
    let mut res = Vec::new();
    for _ in 0..n.to_string().len() {
        res.push(k);
        k = rt(k);
    }
    res
}

fn contains_zero(n: u32) -> bool {
    let mut a = n;
    while a > 0 {
        if a % 10 == 0 {
            return true;
        }
        a /= 10;
    }
    return false;
}

fn main() {
    let ps = er();
    let mut count = 0;
    for p in ps.iter() {
        if contains_zero(*p) {
            continue;
        }
        let ss = rts(*p);
        let mut found_all = true;
        for d in ss {
            if !ps.contains(&d) {
                found_all = false;
                break;
            }
        }
        if found_all {
            println!("{}", p);
            count += 1;
        }
    }
    
    println!("count: {}", count);
}