projecteuler.net/051/main.rs

use std::collections::HashSet;

fn er() -> Vec<u32> {
    let mut nums = Vec::new();
    let size = 1000000;
    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 = Vec::new();
    for i in 2..size {
        if nums[i] { res.push(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 rp(n: u32, is: u32, k: u8) -> u32 {
    let s = n.to_string();
    let mut hs = HashSet::new();
    let mut iss = is;
    while iss > 0 {
        hs.insert(iss%10);
        iss/=10;
    }

    let mut ress = 0;
    let mut index = 0;
    for c in s.chars() {
        ress*=10;
        if !hs.contains(&(index+1)) {
            let cc = c.to_string().parse::<u32>().unwrap();
            //println!("--{} {} {} {}", cc, c, index+1, s);
            ress += cc;
        } else {
            ress += k as u32;
        }
        index+=1;
    }
    return ress;
}

fn replacements(n: u32, is:u32, ps: &HashSet<u32>) -> usize {
    //let mut res = Vec::new();
    //println!("-------");
    let mut res = 0;
    let mut found = false;
    for i in 0..=9 {
        let r=rp(n, is, i);
        if r.to_string().len() < n.to_string().len() { continue; }
        if r == n { found = true; }
        //println!("{} {} {} {}", r, n, is, i);
        if ps.contains(&r) {
            //println!(":: {} {} {} {}", r, n,is,i);
            //res.push(r);
            res+=1;
        }
    }
    if !found { return 0; }
    return res;
}

fn rm(n: u32, _: &Vec<u32>, ps: &HashSet<u32>) -> usize {
    let len = n.to_string().len();
    let rms = lpp(len as u8);
    let mut max_rpls = 0;
    //println!("len {}", rms.len());
    for r in rms.iter() {
        if r.to_string().len() > len {
            break;
        }
        //if !is_diff_tn(*r, len as u32) {
        //    continue;
        //}
        let rpsss = replacements(n, *r, ps);
        //println!("{} {} {}", rpsss, n, *r);
        if rpsss > max_rpls {
            max_rpls = rpsss;
            //println!("-------- {}", *r);
            //for r in rpsss.iter() {
            //    println!("{}", r);
            //}
        }
    }
    return max_rpls;
}

fn b_t_is(n: u32) -> u32 {
    let mut rr = n;
    let mut index = 1;
    let mut res = 0;
    while rr > 0 {
        let c = rr % 2;
        if c == 1 {
            res*=10;
            res+=index;
        }
        index+=1;
        rr/=2;
    }
    return res;
}

fn lpp(n: u8) -> Vec<u32> {
    let mut res = Vec::new();
    let bt = 0;
    let mut tn = 1;
    for _ in 0..n {
        tn *= 2;
    }
    for i in 1..tn {
        res.push(b_t_is(i));
    }

    return res;
}


fn main() {
    //let r = b_t_is(5);
    //println!("{}", r);
    //return;
    //let pmsss = lpp(4);
    //for p in pmsss.iter() {
      //  println!("{}", p);
    //}
    //return;
    let ps = er();
    let mut hs = HashSet::new();
    for p in ps.iter() {
        hs.insert(*p);
    }
    //let r = rp(56003, 13, 1);
    //let id = is_diff(763);
    //println!("...");
    let rms = lpp(6);
    //for r in rs.iter() {
    //    println!("{}", r);
    //}
    //
    //println!(".x.");
    //let v8res = rm(120383, &rms, &hs); // 100109,
    //for p in v8res.iter() {
    //    println!("{}", v8res);
    //}
    //return;
    
    for p in ps.iter() {
        let l = rm(*p, &rms, &hs);
        //println!("{}", p);
        if l == 8 {
            //if *p == 56003 {
            println!("{}", p);
            //}
            break;
        }
    }
    //println!("{}", bs);
    //for r in rsss {
    //    println!("{}", r);
    //}
}