Question

How to check if a number is prime in Kotlin

Answer 1

import kotlin.math.sqrt
import kotlin.random.Random

fun isPrime(num: Int): Int {
    if (num == 0) {
        return 0
    }
    if (num == 1) {
        return 0
    }
    
    for (p in 2..sqrt(num.toDouble()).toInt()) {
        if (num % p == 0) {
            return 0
        }
    }
    
    return 1
}

fun main() {
    for (i in 1..20) {
        val n = Random.nextInt(1, 101)
        if (isPrime(n) == 1) {
            println("$n - Prime")
        } else {
            println("$n - NOT Prime")
        }
    }
}



/*
run:
  
36 - NOT Prime
59 - Prime
90 - NOT Prime
17 - Prime
31 - Prime
100 - NOT Prime
52 - NOT Prime
84 - NOT Prime
66 - NOT Prime
66 - NOT Prime
84 - NOT Prime
13 - Prime
100 - NOT Prime
97 - Prime
31 - Prime
25 - NOT Prime
84 - NOT Prime
26 - NOT Prime
66 - NOT Prime
45 - NOT Prime
  
*/

 

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