52 lines
1.1 KiB
Rust
52 lines
1.1 KiB
Rust
const PRIME_LEN: usize = 10_010;
|
|
const LIMIT: usize = 106_000;
|
|
|
|
struct PrimeCache {
|
|
primes: [u64; PRIME_LEN],
|
|
}
|
|
|
|
impl PrimeCache {
|
|
const fn new() -> Self {
|
|
let mut primes = [0; PRIME_LEN];
|
|
let mut sieve = [true; LIMIT];
|
|
|
|
sieve[0] = false;
|
|
sieve[1] = false;
|
|
|
|
let mut i = 2;
|
|
while i * i < LIMIT {
|
|
if sieve[i] {
|
|
let mut j = i * i;
|
|
while j < LIMIT {
|
|
sieve[j] = false;
|
|
j += i;
|
|
}
|
|
}
|
|
i += 1;
|
|
}
|
|
let mut num = 0;
|
|
let mut j = 0;
|
|
while num < LIMIT && j < PRIME_LEN {
|
|
if sieve[num] {
|
|
primes[j] = num as u64;
|
|
j += 1;
|
|
}
|
|
num += 1;
|
|
}
|
|
Self { primes }
|
|
}
|
|
}
|
|
|
|
static CACHE: PrimeCache = PrimeCache::new();
|
|
|
|
pub fn primes_up_to(upper_bound: u64) -> Vec<u64> {
|
|
let mut nth = 0;
|
|
if upper_bound < 2 {
|
|
return vec![];
|
|
}
|
|
while CACHE.primes[nth] <= upper_bound {
|
|
nth += 1;
|
|
}
|
|
let slice = &CACHE.primes[0..nth];
|
|
slice.to_vec()
|
|
}
|