Kotlin Function: Check Prime Number, Return Boolean

Last update on February 04 2025 08:17:17 (UTC/GMT +8 hours)

Write a Kotlin function that takes an integer as an argument and returns a Boolean indicating whether the number is prime or not. Use explicit return type.

Pre-Knowledge (Before you start!)

• Basic Kotlin Syntax: Familiarity with writing and running Kotlin programs.
• Kotlin Functions: Understanding how to define and call functions in Kotlin.
• Explicit Return Types: Knowledge of specifying return types for functions, such as Boolean.
• Conditional Statements: Ability to use if-else statements to handle different scenarios.
• Loops in Kotlin: Knowledge of using for loops to iterate over a range of numbers.
• Modulo Operator: Awareness of the modulo operator (%) to check divisibility.
• Printing Output: Familiarity with the println() function to display output on the screen.

Hints (Try before looking at the solution!)

• Define the Function.
• Handle Edge Cases.
• Check Divisibility.
• Return Early for Non-Primes.
• Return True for Primes.
• Call the Function.
• Common Errors to Avoid:
  • Forgetting edge cases.
  • Misplacing modulo logic.
  • Not optimizing loop range.

Sample Solution:

Kotlin Code:

fun isPrime(number: Int): Boolean {
    if (number <= 1) {
        return false
    }

    for (i in 2 until number) {
        if (number % i == 0) {
            return false
        }
    }
    return true
}
fun main() {
    val number = 13
    val isNumberPrime = isPrime(number)
    println("Is $number a prime number? $isNumberPrime")
}

Sample Output:

Is 13 a prime number? True

Explanation:

In the above exercise -

• The "isPrime()" function, receives a number parameter of type Int.
• Check if the number is less than or equal to 1, in which case it's not prime, and return false.
• Then, iterate from 2 to one less than the number and check if any number divides the given number without leaving a remainder.
• If find such a divisor, return false, indicating that the number is not prime.
• If the loop ends without finding any divisors, return true, indicating that the number is prime.
• In the "main()" function, we call the "isPrime()" function with a sample number (in this case, 13) and store the result in isNumberPrime. Finally, we print whether the number is prime or not using println.

Kotlin Editor:

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