Creating custom packages in Go - Performance & Efficiency

Time Complexity: Creating custom packages

O(n)

Understanding Time Complexity

When we create custom packages in Go, we want to know how the time it takes to run our code changes as we use these packages more.

We ask: How does adding package code affect the speed of our program?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

package mathutils

func Sum(numbers []int) int {
    total := 0
    for _, num := range numbers {
        total += num
    }
    return total
}

This package function sums all numbers in a list by looping through each one once.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Looping through each number in the input list.
• How many times: Exactly once for each number in the list.

How Execution Grows With Input

As the list gets bigger, the time to add all numbers grows in a straight line.

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

Pattern observation: Doubling the list size doubles the work needed.

Final Time Complexity

Time Complexity: O(n)

This means the time to run grows directly with the number of items we add.

Common Mistake

[X] Wrong: "Using a package always makes code slower because it adds extra steps."

[OK] Correct: The package code runs just like any other code, so its speed depends on what it does, not just that it is a package.

Interview Connect

Understanding how your package code runs helps you write clear and efficient programs, a skill that shows you know how to build good software.

Self-Check

"What if the Sum function used recursion instead of a loop? How would the time complexity change?"