For loop with step and downTo in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of a downTo loop with step

What is the output of this Kotlin code snippet?

Kotlin

fun main() {
    for (i in 10 downTo 1 step 3) {
        print(i)
    }
}

A 1096

B 10741

C 1071

D 1074

💡 Hint

Remember that downTo counts backwards and step skips numbers.

The loop starts at 10 and goes down to 1, stepping by 3 each time. So it prints 10, then 7, then 4, then 1, concatenated as '10741'.

❓ Predict Output

intermediate

Counting down with step 2

What will be printed by this Kotlin code?

Kotlin

fun main() {
    var result = ""
    for (x in 8 downTo 0 step 2) {
        result += x.toString() + ","
    }
    print(result.dropLast(1))
}

A 8,6,4,2,0

B 8,7,6,5,4,3,2,1,0

C 8,6,4,2

D 8,5,2,0

💡 Hint

step 2 means it skips every other number going down.

The loop counts down from 8 to 0 by 2, so it prints 8,6,4,2,0 separated by commas.

🧠 Conceptual

advanced

Understanding step with downTo

Which statement about the Kotlin loop for (i in 15 downTo 5 step 4) is true?

A It prints 15, 11, 7, 3

B It prints 15, 10, 5

C It prints 15, 11, 7

D It prints 15, 14, 13, 12

💡 Hint

step 4 means subtract 4 each time, downTo stops at 5.

Starting at 15, subtract 4 each time: 15, 11, 7. Next would be 3 which is less than 5, so loop stops.

🔧 Debug

advanced

Identify the error in this downTo loop

What error does this Kotlin code produce?

Kotlin

fun main() {
    for (i in 5 downTo 1 step 0) {
        print(i)
    }
}

A IllegalArgumentException: Step must be positive, was 0.

B SyntaxError: Missing colon after for loop

C RuntimeException: Infinite loop detected

D No error, prints 5 4 3 2 1

💡 Hint

Step cannot be zero or negative in Kotlin loops.

Using step 0 is invalid and throws IllegalArgumentException with message about step must be positive.

🚀 Application

expert

Calculate sum using downTo with step

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

Kotlin

fun main() {
    var total = 0
    for (n in 20 downTo 10 step 3) {
        total += n
    }
    print(total)
}

A 75

B 65

C 60

D 62

💡 Hint

Add numbers 20, 17, 14, 11 together.

The loop adds 20 + 17 + 14 + 11 = 62.