Dynamic field names in MATLAB - Time & Space Complexity

Time Complexity: Dynamic field names

O(n)

Understanding Time Complexity

We want to see how the time needed to run code with dynamic field names changes as the input grows.

How does using dynamic field names affect the speed when we add more fields?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

fields = {'a', 'b', 'c', 'd', 'e'};
S = struct();
for i = 1:length(fields)
    fieldName = fields{i};
    S.(fieldName) = i * 10;
end

This code creates a structure and adds fields using names stored in a list, one by one.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: Looping through the list of field names and adding each as a field to the structure.
• How many times: Once for each field name in the list (n times).

How Execution Grows With Input

Each new field is added one after another, so the time grows as we add more fields.

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

Pattern observation: The time needed grows directly with the number of fields added.

Final Time Complexity

Time Complexity: O(n)

This means the time to add fields grows in a straight line as the number of fields increases.

Common Mistake

[X] Wrong: "Adding fields with dynamic names is instant no matter how many fields there are."

[OK] Correct: Each new field requires some work, so more fields mean more time.

Interview Connect

Understanding how dynamic field names affect speed helps you write clear and efficient code, a skill useful in many coding tasks.

Self-Check

"What if we used a nested loop to add fields inside fields? How would the time complexity change?"