projecteuler.net/024/main.rs

//012
//021
//102
//120
//201
//210

type Str = Vec<u8>;

fn pr(s: &Str) {
    for c in s.iter() { print!("{}", c); }
    println!("");
}

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

fn lp(s: &Str, fx: usize, keep_first: bool, mut count: usize) -> usize {
    let kf = 0; //if keep_first { 0usize } else { 1usize };
    for k in (fx + kf)..s.len() {
        let ss = sp(&s, fx, k);
        //count += 1;
        if  ss != *s || keep_first {
            count += 1;
            if count == 1_000_000 {
                //print!("{}\t", count);
                pr(&ss);
            }
        }

        count = lp(&ss, fx + 1, false, count);
    }
    count
}

fn main() {
    let mut s = Vec::new();
    s.push(0);
    s.push(1);
    s.push(2);
    s.push(3);
    s.push(4);
    s.push(5);
    s.push(6);
    s.push(7);
    s.push(8);
    s.push(9);
    lp(&s, 0, true, 0);
}