Repeat function for simple repetition in Kotlin - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ Predict Output

intermediate

Output of repeat function with print

What is the output of this Kotlin code using the repeat function?

Kotlin

fun main() {
    repeat(3) {
        print("Hi")
    }
}

A 3

B

Hi
Hi
Hi

C HiHiHi

D Hi Hi Hi

💡 Hint

The repeat function runs the block multiple times without adding new lines automatically.

The repeat(3) runs the print statement 3 times consecutively. Since print does not add a newline, the output is 'HiHiHi'.

❓ Predict Output

intermediate

Value of variable after repeat loop

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

Kotlin

fun main() {
    var sum = 0
    repeat(4) { i ->
        sum += i
    }
    println(sum)
}

A 6

B 10

C 4

D 0

💡 Hint

The repeat function passes the current iteration index starting from 0.

The loop runs 4 times with i = 0,1,2,3. Sum is 0+1+2+3 = 6.

🔧 Debug

advanced

Identify the error in repeat usage

What error does this Kotlin code produce?

Kotlin

fun main() {
    repeat(3)
        println("Hello")
    println("Done")
}

A SyntaxError: Missing braces for repeat block

B No error, prints Hello three times then Done

C RuntimeException: repeat count must be positive

D Compilation error: Indentation error

💡 Hint

In Kotlin, if the block is a single statement, braces are optional.

The repeat function accepts a single statement without braces. It prints 'Hello' three times, then 'Done'.

❓ Predict Output

advanced

Output with nested repeat calls

What is the output of this Kotlin code with nested repeat calls?

Kotlin

fun main() {
    repeat(2) { i ->
        repeat(2) { j ->
            print("${i}${j} ")
        }
    }
}

A 00 01 10 11

B 00 10 01 11

C 0 1 0 1

D 01 00 11 10

💡 Hint

The outer loop runs for i=0,1 and inner for j=0,1 printing pairs.

The code prints pairs of i and j for each nested loop iteration: 00 01 10 11

🧠 Conceptual

expert

Repeat function behavior with zero count

What happens when you call repeat(0) in Kotlin?

A The block runs once with index 0

B Runs infinitely

C Throws IllegalArgumentException

D The block does not run at all

💡 Hint

Think about how many times the block should run if count is zero.

Calling repeat with 0 means the block runs zero times, so it does not execute at all.

Practice

1. What does the Kotlin repeat function do?

easy

A. Defines a loop that runs until a condition is false

B. Repeats a string multiple times

C. Runs a block of code a specified number of times

D. Creates a list with repeated elements

Solution

1. Step 1: Understand the purpose of repeat

   The repeat function is designed to run a block of code a fixed number of times.

2. Step 2: Compare with other options

   Options B and C describe string or list repetition, which are different functions. Defines a loop that runs until a condition is false describes a conditional loop, not repeat.

3. Final Answer:

   Runs a block of code a specified number of times -> Option C

4. Quick Check:

   repeat = run code N times [OK]

Hint: Remember: repeat runs code block N times [OK]

Common Mistakes:

• Confusing repeat with string repetition
• Thinking repeat creates collections
• Mixing repeat with while or for loops

2. Which of the following is the correct syntax to repeat a print statement 3 times in Kotlin?

easy

A. repeat 3 { println("Hello") }

B. repeat(3) { println("Hello") }

C. repeat(3); println("Hello")

D. repeat {3} println("Hello")

Solution

1. Step 1: Check the function call syntax

   The repeat function requires parentheses around the number of repetitions and a lambda block with curly braces.

2. Step 2: Validate each option

   repeat(3) { println("Hello") } correctly uses repeat(3) { ... }. Options B, C, and D have syntax errors or misplaced braces.

3. Final Answer:

   repeat(3) { println("Hello") } -> Option B

4. Quick Check:

   repeat(number) { code } syntax [OK]

Hint: Use parentheses for count and braces for code block [OK]

Common Mistakes:

• Omitting parentheses around the count
• Using semicolon instead of braces
• Placing braces incorrectly

3. What will be the output of this Kotlin code?

repeat(4) { i -> println(i * 2) }

medium

A. 0 1 2 3

B. 2 4 6 8

C. 1 2 3 4

D. 0 2 4 6

Solution

1. Step 1: Understand the index parameter

   The lambda receives i from 0 to 3 (4 times). Each iteration prints i * 2.

2. Step 2: Calculate each output line

   For i=0: 0*2=0, i=1: 2, i=2: 4, i=3: 6. So output lines are 0, 2, 4, 6.

3. Final Answer:

   0 2 4 6 -> Option D

4. Quick Check:

   repeat with index * 2 = 0 2 4 6 [OK]

Hint: Index starts at 0 in repeat lambda [OK]

Common Mistakes:

• Starting index at 1 instead of 0
• Forgetting to multiply by 2
• Confusing output with index values

4. Identify the error in this Kotlin code:

repeat(3) 
 println("Hi")

medium

A. Missing curly braces for the code block

B. repeat cannot be used with println

C. repeat requires a semicolon after the number

D. The number 3 should be a string

Solution

1. Step 1: Check the syntax of repeat

   The repeat function expects a lambda block enclosed in curly braces after the count.

2. Step 2: Identify the missing braces

   The code has no braces around println("Hi"), so it is a syntax error.

3. Final Answer:

   Missing curly braces for the code block -> Option A

4. Quick Check:

   repeat needs braces { } for code [OK]

Hint: Always use braces { } after repeat(count) [OK]

Common Mistakes:

• Omitting braces for single statement
• Adding semicolon after number
• Passing number as string

5. How can you use repeat to create a list of squares of numbers from 0 to 4 in Kotlin?

hard

A. val squares = mutableListOf<Int>(); repeat(5) { squares.add(it * it) }

B. val squares = repeat(5) { it * it }

C. val squares = List(5) { repeat(it * it) }

D. val squares = repeat(5) { println(it * it) }

Solution

1. Step 1: Understand repeat usage for list building

   The repeat function runs code multiple times but does not return a list itself.

2. Step 2: Check each option's approach

   val squares = mutableListOf<Int>(); repeat(5) { squares.add(it * it) } creates a mutable list and adds squares inside repeat, which works. val squares = repeat(5) { it * it } tries to assign repeat's result directly, which is Unit (no list). val squares = List(5) { repeat(it * it) } misuses List and repeat. val squares = repeat(5) { println(it * it) } only prints values, no list created.

3. Final Answer:

   val squares = mutableListOf<Int>(); repeat(5) { squares.add(it * it) } -> Option A

4. Quick Check:

   repeat + add to list = correct list [OK]

Hint: Use repeat to add items to a mutable list [OK]

Common Mistakes:

• Expecting repeat to return a list
• Using repeat inside List constructor incorrectly
• Only printing values without storing