Comments and documentation markup in Swift - Time & Space Complexity

Time Complexity: Comments and documentation markup

O(n)

Understanding Time Complexity

We want to understand how adding comments and documentation affects the time it takes for a program to run.

Does writing comments change how fast the program works?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

    /// Calculates the sum of numbers from 1 to n.
    /// - Parameter n: The upper limit number.
    /// - Returns: The sum as an integer.
    func sumUpTo(_ n: Int) -> Int {
        var total = 0
        for i in 1...n {
            total += i
        }
        return total
    }
    

This function adds numbers from 1 up to n and returns the total. It includes comments explaining what it does.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: The for-loop that adds each number from 1 to n.
• How many times: Exactly n times, once for each number.

How Execution Grows With Input

As n grows, the number of additions grows the same way.

Input Size (n)	Approx. Operations
10	10 additions
100	100 additions
1000	1000 additions

Pattern observation: The work grows directly with n; double n means double the additions.

Final Time Complexity

Time Complexity: O(n)

This means the time to run grows in a straight line with the size of n.

Common Mistake

[X] Wrong: "Adding comments makes the program slower because it adds more lines to run."

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

Interview Connect

Understanding that comments do not affect how fast code runs helps you focus on what really matters when writing efficient programs.

Self-Check

"What if we replaced the for-loop with a formula that calculates the sum directly? How would the time complexity change?"