Gets primes by Sieve of Eratosthenes

sieve_primes.swift

func findPrimes(upTo limit: Int) -> [Int] {
   guard limit > 1 else { return [] }
    
    var sieve = Array(repeating: true, count: limit + 1)
    
    sieve[0] = false
    sieve[1] = false
    
    for i in 2...limit where sieve[i] {
        for j in stride(from: i*i, through: limit, by: i) {
            print(i, j)
            sieve[j] = false
        }
    }
    
    return sieve.enumerated().compactMap { $1 == true ? $0 : nil }
}