If statement in C - Time & Space Complexity

Time Complexity: If statement

O(1)

Understanding Time Complexity

We want to see how the time it takes to run an if statement changes as the input changes.

Does the if statement make the program slower when input grows?

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

int checkNumber(int n) {
    if (n > 0) {
        return 1;
    } else {
        return 0;
    }
}
    

This code checks if a number is positive and returns 1 if true, otherwise 0.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: A single if condition check.
• How many times: Exactly once per function call.

How Execution Grows With Input

Checking the if condition takes the same time no matter what number we give.

Input Size (n)	Approx. Operations
10	1 check
100	1 check
1000	1 check

Pattern observation: The time stays the same even if the input number grows.

Final Time Complexity

Time Complexity: O(1)

This means the if statement takes the same amount of time no matter how big the input is.

Common Mistake

[X] Wrong: "If statements take longer when the input number is bigger."

[OK] Correct: The if condition is just one check and does not repeat or grow with input size.

Interview Connect

Understanding that simple decisions like if statements run quickly helps you explain how your code behaves in real situations.

Self-Check

"What if we added a loop inside the if statement? How would the time complexity change?"