projecteuler.net/043/main.rs

use std::collections::HashSet;
use std::collections::VecDeque;

type Str = VecDeque<u8>;
type Res = HashSet<u64>;


fn nstr(n: u64) -> Str {
    let mut res = Str::new();
    let mut nn = n;
    while nn > 0 {
        res.push_front((nn % 10) as u8);
        nn /= 10;
    }
    res
}


fn strn(s: &Str) -> u64 {
    let mut res = 0;
    for d in s.iter() {
        res *= 10;
        res += *d as u64;
    }
    res
}

fn strnn(s: &Str, p: usize) -> u64 {
    let mut ss = Str::new();
    for q in p..p + 3 {
        ss.push_back(*s.get(q).unwrap());
    }
    return strn(&ss);
}


fn test(s: &Str) -> bool {
   // {
    //    let nnn = strn(s);
    //    if nnn == 1406357289 {
    //        println!("!!{}", nnn);
    //    }
    //}
    let ps = [2,3,5,7,11,13,17];
    for k in 1..8 {
        let n = strnn(s, k);
        //println!("{}", n);
        if n % ps[(k - 1)] != 0 {
            //println!("{} {}", n, ps[k-1]);
            return false;
        }
    }
    return true;
}

fn sp(s: &Str, fx: usize, k: usize) -> Str {
    let mut res = Str::new();
    for i in 0..fx {
        res.push_back(s[i]);
    }
    res.push_back(s[k]);
    for i in fx..s.len() {
        if i != k { res.push_back(s[i]); }
    }
    res
}

fn lp(s: &Str, fx: usize, keep_first: bool, hs: &mut Res) {
    let kf = 0; //if keep_first { 0usize } else { 1usize };
    for k in (fx + kf)..s.len() {
        let ss = sp(&s, fx, k);
        if  ss != *s || keep_first {
            if test(&ss) {
                let n = strn(&ss);
                hs.insert(n);
            }
        }
        lp(&ss, fx + 1, false, hs);
    }
}

fn main() {
    let mut hs = HashSet::new();
    let s = nstr(1234567890);
    let mut sum = 0u64;
    //let mut ttt = 9876543210u64;
    //{
    //    let rrrr = nstr(1406357289);
    //    let tt = test(&rrrr);
    //    println!("{}",  tt);
    //}
    //return;
    lp(&s, 0, true, &mut hs);
    for h in hs.iter() {
        println!("{}", h);
        sum += *h;
    }
    println!("{}", sum);
}