Comments and documentation syntax in Kotlin - Time & Space Complexity

Time Complexity: Comments and documentation syntax

O(1)

Understanding Time Complexity

We look at how adding comments and documentation affects the time it takes to run Kotlin code.

Does writing comments change how fast the program runs?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

// This function adds two numbers
fun add(a: Int, b: Int): Int {
    return a + b // return the sum
}

/**
 * Multiplies two numbers
 * @param a first number
 * @param b second number
 * @return product of a and b
 */
fun multiply(a: Int, b: Int): Int {
    return a * b
}
    

This code shows comments and documentation around simple functions.

Identify Repeating Operations

Look for any repeated work that might affect speed.

• Primary operation: Simple math operations (addition, multiplication)
• How many times: Once per function call

Comments do not repeat or run; they are ignored by the computer.

How Execution Grows With Input

Adding comments does not add steps when the program runs.

Input Size (n)	Approx. Operations
10	1 addition or multiplication
100	1 addition or multiplication
1000	1 addition or multiplication

Pattern observation: The number of operations does not grow with input size, and comments do not add to this.

Final Time Complexity

Time Complexity: O(1)

This means the program runs in constant time per function call, regardless of comments.

Common Mistake

[X] Wrong: "Adding many comments will slow down my program."

[OK] Correct: Comments are ignored when running code, so they do not affect speed at all.

Interview Connect

Understanding that comments do not affect performance shows you know how code runs behind the scenes, a useful skill for writing clean and efficient programs.

Self-Check

"What if comments were replaced by code that prints messages during execution? How would the time complexity change?"

Practice

1. Which of the following is the correct way to write a single-line comment in Kotlin?

easy

A. /* This is a single-line comment */

B.

C. // This is a single-line comment

D. # This is a single-line comment

Solution

1. Step 1: Identify single-line comment syntax in Kotlin

   Kotlin uses // to start a single-line comment.

2. Step 2: Compare options

   // This is a single-line comment uses //, which is correct. /* This is a single-line comment */ is for multi-line comments. <!-- This is a single-line comment --> is HTML style. # This is a single-line comment is used in some scripting languages but not Kotlin.

3. Final Answer:

   // This is a single-line comment -> Option C

4. Quick Check:

   Single-line comment = // [OK]

Hint: Single-line comments start with // in Kotlin [OK]

Common Mistakes:

• Using /* */ for single-line comments
• Using # or which are not Kotlin comments
• Confusing multi-line and single-line comment syntax

2. Which of the following is the correct syntax for a multi-line comment in Kotlin?

easy

A. /* This is a multi-line comment */

B.

C. /** This is a multi-line comment */

D. // This is a multi-line comment

Solution

1. Step 1: Recall multi-line comment syntax in Kotlin

   Kotlin uses /* ... */ to write multi-line comments.

2. Step 2: Analyze options

   /* This is a multi-line comment */ correctly uses /* ... */. // This is a multi-line comment is single-line comment syntax. /** This is a multi-line comment */ is documentation comment syntax. <!-- This is a multi-line comment --> is HTML comment syntax.

3. Final Answer:

   /* This is a multi-line comment */ -> Option A

4. Quick Check:

   Multi-line comment = /* ... */ [OK]

Hint: Multi-line comments use /* and */ to start and end [OK]

Common Mistakes:

• Using // for multi-line comments
• Confusing documentation comments /** */ with regular multi-line comments
• Using HTML style comments

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

fun main() {
    // println("Hello")
    println("World")
}

medium

A. Hello
World

B. World

C. Hello

D. No output

Solution

1. Step 1: Understand comment effect on code execution

   The line // println("Hello") is a comment, so it does not run.

2. Step 2: Identify which println runs

   Only println("World") runs, so output is "World".

3. Final Answer:

   World -> Option B

4. Quick Check:

   Commented code does not run = World [OK]

Hint: Commented lines do not execute, only uncommented print runs [OK]

Common Mistakes:

• Thinking commented println runs
• Expecting both lines to print
• Confusing comment syntax and output

4. Identify the error in the following Kotlin code snippet:

fun main() {
    /* This is a comment
    println("Hello")
}

medium

A. No error, code runs fine

B. Incorrect single-line comment syntax

C. Missing quotation marks in println

D. Missing closing */ for multi-line comment

Solution

1. Step 1: Check multi-line comment syntax

   The comment starts with /* but does not have a closing */.

2. Step 2: Understand impact of missing closing comment

   Without closing */, the compiler treats the rest as comment, causing syntax error.

3. Final Answer:

   Missing closing */ for multi-line comment -> Option D

4. Quick Check:

   Multi-line comments must close with */ [OK]

Hint: Always close multi-line comments with */ [OK]

Common Mistakes:

• Forgetting to close multi-line comments
• Confusing single-line and multi-line comment syntax
• Assuming code inside unclosed comment runs

5. Which comment style should you use in Kotlin to write documentation that tools can extract to generate API docs?

hard

A. /** This is a documentation comment */

B. /* This is a documentation comment */

C. // This is a documentation comment

D.

Solution

1. Step 1: Identify documentation comment syntax in Kotlin

   Kotlin uses /** ... */ for documentation comments that tools can parse.

2. Step 2: Compare with other comment types

   // This is a documentation comment is single-line comment syntax. /* This is a documentation comment */ is regular multi-line comment syntax. <!-- This is a documentation comment --> is HTML comment syntax.

3. Final Answer:

   /** This is a documentation comment */ -> Option A

4. Quick Check:

   Documentation comments use /** ... */ [OK]

Hint: Use /** ... */ for documentation comments in Kotlin [OK]

Common Mistakes:

• Using // or /* */ for documentation comments
• Confusing documentation comments with regular comments
• Using HTML comment style by mistake