Vararg parameters in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of function with vararg parameter

What is the output of this Kotlin code using a vararg parameter?

Kotlin

fun printAll(vararg messages: String) {
    for (m in messages) print("$m ")
}

fun main() {
    printAll("Hi", "there", "Kotlin")
}

A [Hi, there, Kotlin]

B Hi,there,Kotlin

C

Hi
there
Kotlin

D Hi there Kotlin

💡 Hint

Remember that the function prints each message followed by a space.

The function loops through each string in the vararg and prints it with a trailing space, so the output is all words separated by spaces on the same line.

🧠 Conceptual

intermediate

Vararg parameter usage in Kotlin

Which statement about vararg parameters in Kotlin is true?

A Vararg parameters must always be the first parameter in the function.

B A function can have multiple vararg parameters.

C Vararg parameters allow passing zero or more arguments of the specified type.

D You cannot pass an array to a vararg parameter.

💡 Hint

Think about how many arguments you can pass to a vararg parameter.

Vararg parameters let you pass zero or more arguments of the specified type. Only one vararg parameter is allowed per function, and it must be the last parameter. You can pass an array using the spread operator.

❓ Predict Output

advanced

Output with vararg and spread operator

What is the output of this Kotlin code snippet?

Kotlin

fun sumAll(vararg numbers: Int): Int {
    var sum = 0
    for (n in numbers) sum += n
    return sum
}

fun main() {
    val nums = intArrayOf(1, 2, 3)
    println(sumAll(*nums, 4))
}

A Compilation error

B 10

C 7

D 6

💡 Hint

The spread operator (*) passes array elements as individual arguments.

The array nums contains 1, 2, 3. Using *nums passes these as separate arguments along with 4, so sumAll sums 1+2+3+4 = 10.

🔧 Debug

advanced

Identify the error with vararg usage

What error does this Kotlin code produce?

Kotlin

fun printNumbers(prefix: String, vararg nums: Int) {
    for (n in nums) print("$prefix$n ")
}

fun main() {
    printNumbers(prefix = "#", 1, 2, 3)
}

A Prints: #1 #2 #3

B Runtime error: prefix not found

C Compilation error: missing argument for prefix

D Compilation error: vararg parameter must be the last parameter

💡 Hint

Check the order of parameters when using vararg.

In Kotlin, the vararg parameter must be the last parameter in the function declaration. Here, prefix comes before vararg, which is correct, so the code compiles and prints the output.

🚀 Application

expert

Count total characters using vararg strings

What is the value of totalChars after running this Kotlin code?

Kotlin

fun countChars(vararg words: String): Int {
    return words.sumOf { it.length }
}

fun main() {
    val totalChars = countChars("Kotlin", "is", "fun")
}

A 11

B 10

C 12

D Compilation error

💡 Hint

Add the lengths of all strings passed as arguments.

The strings are "Kotlin" (6 letters), "is" (2 letters), and "fun" (3 letters). Total is 6 + 2 + 3 = 11.