エラトステネスのふるい(中間生成物)

SieveOfEratosthenes.swift

import Foundation

let range = 1000

var primeNumbers: [Int] = []

func sieveOfEratosthenes() {
    for number in 0...range {
        if number == 0 || number == 1 {
            primeNumbers.removeFirst()
            continue
        }

        if number * number > range {
            break
        }

        primeNumbers = primeNumbers.filter { remain in
            if remain == number {
                return true // ここでのprimeNumbersの最小の値は素数
            } else {
                return !(remain % number == 0) // remainより大きいremainの倍数を除外
            }
        }
    }
}

func main() {
    primeNumbers = Array(0...range)
    sieveOfEratosthenes()
    print("Prime Numbers:")
    print(primeNumbers)
}

main()