-
Notifications
You must be signed in to change notification settings - Fork 0
/
sieve.rs
49 lines (47 loc) · 1.12 KB
/
sieve.rs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
struct SimpleSieve {
sieve: Vec<bool>,
current_index: usize,
last_prime: usize,
}
impl SimpleSieve {
fn new(size: usize) -> SimpleSieve {
let mut ret = SimpleSieve {
sieve: Vec::with_capacity(if size < 3 { 3 } else { size }),
current_index: 0,
last_prime: 0,
};
for _ in 0..size {
ret.sieve.push(true);
}
ret.sieve[0] = false;
ret.sieve[1] = false;
ret.sieve[2] = true;
ret
}
}
impl Iterator for SimpleSieve {
type Item = usize;
fn next(&mut self) -> Option<usize> {
let mut i = self.current_index;
while i < self.sieve.len() && !self.sieve[i] {
i+=1;
}
self.current_index = i;
if i < self.sieve.len() {
//found a prime
let prime = i;
while i < self.sieve.len() {
self.sieve[i] = false;
i += prime;
}
Some(prime)
} else {
None
}
}
}
fn main() {
for prime in SimpleSieve::new(1000) {
println!("{:?}",prime);
}
}