Pop Operation on Stack in DSA C - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does the pop operation do in a stack?

It removes the top element from the stack and returns it, reducing the stack size by one.

beginner

What happens if you try to pop from an empty stack?

This is called stack underflow. It means there is no element to remove, and the operation should handle this error.

beginner

In C, which variable usually tracks the top of the stack for pop operation?

An integer variable called top is used to track the index of the top element in the stack array.

beginner

What is the time complexity of the pop operation on a stack?

The pop operation runs in O(1) time because it only removes the top element without traversing the stack.

beginner

Show the basic steps of the pop operation on a stack implemented with an array.

1. Check if the stack is empty (top == -1).<br>2. If not empty, get the element at stack[top].<br>3. Decrease top by 1.<br>4. Return the popped element.

What does the pop operation return when the stack is empty?

A An error or special value indicating underflow

B The bottom element of the stack

C The last pushed element without removing it

D The size of the stack

Pop on an empty stack causes underflow, so it returns an error or special value.

Which variable is commonly used to track the top element in a stack implemented with an array?

A tail

B head

C top

D count

The variable 'top' tracks the index of the top element in the stack.

What is the time complexity of the pop operation on a stack?

A O(n^2)

B O(log n)

C O(n)

D O(1)

Pop removes the top element directly, so it runs in constant time O(1).

After popping an element, what happens to the 'top' variable?

A It decreases by 1

B It stays the same

C It increases by 1

D It resets to zero

The 'top' decreases by 1 to point to the new top element after pop.

Which of the following is NOT a step in the pop operation?

A Check if stack is empty

B Increase the top index

C Return the top element

D Decrease the top index

Pop decreases the top index; increasing it is incorrect.

Explain the pop operation on a stack implemented using an array.

Think about what happens when you remove the last added item.

Describe what stack underflow means and how it relates to the pop operation.

Consider what happens if you pop too many times.