Repeat function for simple repetition in Kotlin - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the Kotlin repeat() function do?

The repeat() function runs a block of code a specified number of times. It's a simple way to repeat actions without writing loops manually.

beginner

How do you use repeat() to print "Hello" 3 times?

You write repeat(3) { println("Hello") }. This runs the print statement 3 times.

beginner

What parameter does the repeat() function take?

It takes an integer that tells how many times to repeat the code block.

intermediate

Can you access the current iteration index inside repeat()?

Yes, repeat() provides the current iteration index (starting from 0) as a parameter to the lambda block.

beginner

Write a Kotlin repeat() example that prints numbers 0 to 4.

Use repeat(5) { println(it) }. The it is the current index from 0 to 4.

What does the repeat(4) { println("Hi") } code do?

A Prints "Hi" 4 times

B Prints "Hi" once

C Prints numbers 1 to 4

D Causes an error

The repeat() function runs the code block 4 times, printing "Hi" each time.

What is the type of the parameter passed to repeat()?

A String

B Int

C Double

D Boolean

The repeat() function takes an integer to specify how many times to repeat.

Inside repeat(n) { }, what does it represent?

A The current repetition index starting at 0

B The total number of repetitions

C The last printed value

D The function name

it is the current index of the repetition, starting from 0 up to n-1.

Which of these is a correct way to repeat a block 5 times in Kotlin?

A repeat(5); { /* code */ }

B repeat { 5 /* code */ }

C repeat(5) -> { /* code */ }

D repeat(5) { /* code */ }

The correct syntax is repeat(5) { /* code */ }.

What will this code print? repeat(3) { println(it * 2) }

A 0 1 2

B 1 2 3

C 0 2 4

D 2 4 6

The code prints the current index multiplied by 2: 0*2=0, 1*2=2, 2*2=4.

Explain how the Kotlin repeat() function works and give a simple example.

Think about how you would say 'do this 3 times' in code.

How can you use the iteration index inside the repeat() function? Provide a code snippet.

Remember 'it' is the current count starting at zero.

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