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65 lines
1.4 KiB
65 lines
1.4 KiB
1 year ago
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use std::collections::HashSet;
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fn er() -> HashSet<u32> {
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let mut nums = Vec::new();
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let size = 1_000_000;
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for n in 0..size+1 { nums.push(true); }
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let mut p = 1;
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while true {
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let mut found = false;
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for i in p+1..size {
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if nums[i] {
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found = true;
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p = i;
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break;
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}
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}
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if !found { break; }
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for i in (2 * p .. size).step_by(p) {
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nums[i] = false;
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}
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}
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let mut res = HashSet::new();
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for i in 2..size {
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if nums[i] { res.insert(i as u32); }
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}
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return res;
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}
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fn trl(n: u32) -> u32 {
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let s = n.to_string();
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let mut chars = s.chars();
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let f = chars.next().unwrap();
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//chars.next_back();
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let mut res = String::from(chars.as_str());
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res.parse::<u32>().unwrap()
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}
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fn test(p: u32, hs: &HashSet<u32>) -> bool {
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let mut tl = p;
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while tl > 10 {
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if !hs.contains(&tl) { return false; }
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tl = trl(tl);
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}
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if !hs.contains(&tl) { return false; }
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let mut tr = p;
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while tr > 0 {
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if !hs.contains(&tr) { return false; }
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tr /= 10;
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}
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return true;
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}
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fn main() {
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let hs = er();
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let mut sum = 0;
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for p in hs.iter() {
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if *p < 10 { continue; }
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if test(*p, &hs) {
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println!("{}", p);
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sum += p;
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}
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}
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println!("sum: {}", sum);
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}
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