For loop with ranges in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a simple for loop with range

What is the output of this Kotlin code?

Kotlin

fun main() {
    for (i in 1..3) {
        print(i)
    }
}

A 0123

B 1 2 3

C 123

D 3 2 1

💡 Hint

Remember that the range 1..3 includes both 1 and 3, and print() does not add spaces or newlines.

The for loop iterates over 1, 2, and 3. The print function outputs each number without spaces or newlines, so the output is '123'.

❓ Predict Output

intermediate

For loop with step in range

What is the output of this Kotlin code?

Kotlin

fun main() {
    for (i in 0..6 step 2) {
        print(i)
    }
}

A 135

B 0123456

C 246

D 0246

💡 Hint

The step keyword skips numbers by the given step size.

The loop starts at 0 and goes up to 6, stepping by 2 each time, so it prints 0, 2, 4, 6 without spaces.

❓ Predict Output

advanced

For loop with downTo and step

What is the output of this Kotlin code?

Kotlin

fun main() {
    for (i in 10 downTo 2 step 3) {
        print(i)
    }
}

A 1074

B 108642

C 10374

D 109642

💡 Hint

downTo counts backwards, step skips numbers by the step size.

The loop starts at 10, then 7, then 4, then stops because next step 1 is less than 2. So output is '1074'.

🔧 Debug

advanced

Identify the error in the for loop with range

What error does this Kotlin code produce?

Kotlin

fun main() {
    for (i in 1..5 step) {
        print(i)
    }
}

A SyntaxError: Expecting an expression after 'step'

B No error, prints 12345

C TypeError: step must be an integer

D RuntimeException: Invalid range

💡 Hint

Check the syntax of the step keyword in the range expression.

The 'step' keyword requires a number after it. Missing the number causes a syntax error.

🧠 Conceptual

expert

Number of iterations in a for loop with range and step

How many times does this Kotlin for loop run?

Kotlin

fun main() {
    var count = 0
    for (i in 5 downTo 0 step 2) {
        count++
    }
    println(count)
}

A 5

B 3

C 4

D 6

💡 Hint

List the numbers generated by the range and count them.

The loop runs for i = 5, 3, 1. It stops before reaching -1. So it runs 3 times.