Sieve of Eratosthenes

sieve.rs

 //
 // Let A be an array of Boolean values, indexed by integers 2 to n,
 // initially all set to true.
 //
 // for i = 2, 3, 4, ..., not exceeding √n:
 //   if A[i] is true:
 //     for j = i**2, i**2+i, i**2+2i, i**2+3i, ..., not exceeding n:
 //       A[j] := false.
 //
 // Output: all i such that A[i] is true.


fn sieve(n: u32) -> Vec<usize> {
    let mut checks: Vec<bool> = vec![true; (n + 1) as usize];
    let max_val = (((n as f32).sqrt()).round() as u32);
    for i in 2..max_val {
        let mut counter = 0;
        if checks[i as usize] == true {
            loop {
                let j = i.pow(2) + counter * i;
                counter += 1;
                if j > n {
                    break
                }
                checks[j as usize] = false;
            }
        }
    }
    let vec: Vec<usize> = checks
        .iter()
        .enumerate()
        .filter(| &(_, b) | { *b })
        .map(| (a, _) | { a })
        .collect();

    vec
}

fn main() {
    println!("{:?}", sieve(1346));
}