Created
January 17, 2018 20:49
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Sieve of Eratosthenes
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// | |
// 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)); | |
} |
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