Continue statement - Time & Space Complexity

Time Complexity: Continue statement

O(n)

Understanding Time Complexity

Let's see how the continue statement affects the time complexity of a loop in C.

We want to know how the number of steps changes as the input size grows.

Scenario Under Consideration

Analyze the time complexity of the following code snippet.

for (int i = 0; i < n; i++) {
    if (i % 2 == 0) {
        continue;
    }
    // Some constant time operation
    sum += i;
}
    

This code loops from 0 to n-1, skips even numbers using continue, and sums odd numbers.

Identify Repeating Operations

Identify the loops, recursion, array traversals that repeat.

• Primary operation: The for-loop runs from 0 to n-1.
• How many times: The loop runs n times, but the sum operation runs only for odd i values (about n/2 times).

How Execution Grows With Input

Even though some steps are skipped, the loop still checks every number up to n.

Input Size (n)	Approx. Operations
10	10 loop checks, ~5 sum operations
100	100 loop checks, ~50 sum operations
1000	1000 loop checks, ~500 sum operations

Pattern observation: The total steps grow roughly in a straight line as n grows.

Final Time Complexity

Time Complexity: O(n)

This means the time to run the loop grows directly with the size of n, even with the continue skipping some steps.

Common Mistake

[X] Wrong: "Since continue skips some steps, the loop runs faster and time complexity is less than O(n)."

[OK] Correct: The loop still checks every number once, so the total steps still grow with n. Skipping inside the loop does not reduce the number of loop iterations.

Interview Connect

Understanding how control statements like continue affect loops helps you explain code efficiency clearly and confidently in interviews.

Self-Check

What if we replaced the continue with a nested loop inside the if-block? How would the time complexity change?

Practice

1. What does the continue statement do inside a loop in C?

easy

A. Skips the rest of the current loop iteration and moves to the next iteration

B. Stops the entire loop immediately

C. Exits the current function

D. Restarts the program from the beginning

Solution

1. Step 1: Understand the role of continue

   The continue statement does not stop the loop but skips the remaining code in the current iteration.

2. Step 2: Effect on loop execution

   After continue, the loop immediately proceeds to the next iteration, ignoring any code below it in the current cycle.

3. Final Answer:

   Skips the rest of the current loop iteration and moves to the next iteration -> Option A

4. Quick Check:

   continue skips current iteration [OK]

Hint: Remember: continue skips current loop step, not whole loop [OK]

Common Mistakes:

• Confusing continue with break
• Thinking continue exits the function
• Assuming continue restarts the program

2. Which of the following is the correct syntax to use continue inside a for loop in C?

easy

A. continue;

B. continue()

C. continue{}

D. continue[]

Solution

1. Step 1: Recall correct statement syntax

   In C, continue is a statement and must end with a semicolon.

2. Step 2: Identify valid syntax

   Only continue; is valid; parentheses, braces, or brackets are incorrect.

3. Final Answer:

   continue; -> Option A

4. Quick Check:

   Statement ends with semicolon [OK]

Hint: Statements end with semicolon; continue is no exception [OK]

Common Mistakes:

• Adding parentheses after continue
• Using braces or brackets with continue
• Omitting the semicolon

3. What is the output of the following C code?

for (int i = 1; i <= 5; i++) {
    if (i == 3) continue;
    printf("%d ", i);
}

medium

A. 1 2 3 4 5

B. 1 2 4 5

C. 1 2 3 4

D. 2 3 4 5

Solution

1. Step 1: Analyze loop iterations

   The loop runs i from 1 to 5. When i equals 3, the continue statement skips printing.

2. Step 2: Determine printed values

   Values 1, 2, 4, and 5 are printed with spaces. The number 3 is skipped.

3. Final Answer:

   1 2 4 5 -> Option B

4. Quick Check:

   continue skips printing 3 [OK]

Hint: Skip printing when continue triggers, others print normally [OK]

Common Mistakes:

• Including the skipped number in output
• Confusing continue with break
• Ignoring the loop condition

4. Identify the error in this code snippet using continue:

int i = 0;
while (i < 5) {
    if (i == 2)
        continue;
    printf("%d ", i);
    i++;
}

medium

A. Syntax error: continue cannot be used in while loops

B. The printf statement is unreachable

C. The loop will run infinitely because 'i' is not incremented when i == 2

D. The variable 'i' is not declared properly

Solution

1. Step 1: Understand loop flow with continue

   When i equals 2, continue skips the rest of the loop body, so i++ is not executed.

2. Step 2: Consequence of skipping i++

   Since i is not incremented at i == 2, the loop condition remains true forever, causing an infinite loop.

3. Final Answer:

   The loop will run infinitely because 'i' is not incremented when i == 2 -> Option C

4. Quick Check:

   continue skips i++ causing infinite loop [OK]

Hint: Always increment loop variable before continue to avoid infinite loops [OK]

Common Mistakes:

• Thinking continue causes syntax error
• Assuming printf is unreachable
• Ignoring loop variable increment

5. How can you modify this code to print only odd numbers from 1 to 10 using continue?

for (int i = 1; i <= 10; i++) {
    printf("%d ", i);
}

hard

A. Add if (i == 2) continue; before printf

B. Add if (i % 2 != 0) continue; before printf

C. Replace printf with if (i % 2 != 0) printf("%d ", i);

D. Add if (i % 2 == 0) continue; before printf

Solution

1. Step 1: Identify condition to skip even numbers

   Even numbers satisfy i % 2 == 0. Using continue here skips printing even numbers.

2. Step 2: Place continue before printf

   Adding if (i % 2 == 0) continue; before printf skips printing even numbers, so only odd numbers print.

3. Final Answer:

   Add if (i % 2 == 0) continue; before printf -> Option D

4. Quick Check:

   continue skips even numbers, prints odd [OK]

Hint: Skip even numbers with continue to print only odds [OK]

Common Mistakes:

• Skipping odd numbers instead of even
• Using continue after printf
• Incorrect condition for even numbers