Question

How to check if a number is prime in Swift

Answer 1

import Foundation

func isPrime(_ num: Int) -> Bool {
    if num == 0 || num == 1 {
        return false
    }
    
    for p in 2...Int(sqrt(Double(num))) {
        if num % p == 0 {
            return false
        }
    }
    
    return true
}

for _ in 1...20 {
    let n = Int.random(in: 1...200)
    if isPrime(n) {
        print("\(n) - Prime")
    } else {
        print("\(n) - NOT Prime")
    }
}



/*
run:
 
160 - NOT Prime
88 - NOT Prime
163 - Prime
49 - NOT Prime
92 - NOT Prime
129 - NOT Prime
101 - Prime
96 - NOT Prime
79 - Prime
112 - NOT Prime
104 - NOT Prime
178 - NOT Prime
90 - NOT Prime
103 - Prime
160 - NOT Prime
69 - NOT Prime
175 - NOT Prime
178 - NOT Prime
23 - Prime
26 - NOT Prime

*/

 

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