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Practice

Stack: Data Entered Last Comes Out First

A stack is a data structure where the last element added is the first to be removed, which is known as Last In First Out (LIFO).

In simple terms, it works like stacking books where you take the book from the top first.

A stack allows data to be added or removed in a limited fashion and is used in various program functionalities such as browser history, undo functions, and more.


Basic Operations of a Stack​

A stack consists of the following main operations:

  • Push: Adds a new element to the top of the stack.

  • Pop: Removes the most recently added element from the stack and returns that element.

  • Peek (or Top): Returns the top element of the stack without removing it.

  • IsEmpty: Checks if the stack is empty.


How Can a Stack Be Implemented?​

In Python, a simple stack can be implemented using a list.

Stack Usage Example
# Initialize stack
stack = []

# Push elements
stack.append(1)
stack.append(2)
stack.append(3)

# Peek at the top element
print(stack[-1])
# Output: 3

# Pop the top element
print(stack.pop())
# Output: 3
print(stack.pop())
# Output: 2

# Check if the stack is empty
print(len(stack) == 0)
# Output: False

You can find a more detailed stack implementation using Class in the code editor on the right.

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