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Stack

A linear data structure that follows the LIFO principle

Stack

A stack is a linear data structure that follows the Last In, First Out (LIFO) principle. Think of it like a stack of plates - you can only add or remove plates from the top.

Core Concept

LIFO Principle: The last element added to the stack will be the first one to be removed.

Visualization of Last In First Out

Real-world Example: Imagine stacking plates in a cafeteria. When you add a plate, you place it on top. To remove a plate, you take the topmost one first.

Key Properties

Linear Structure

Elements are arranged sequentially, with each element connected to adjacent ones.

Single Access Point

All operations happen at the 'top' of the stack. No direct access to middle or bottom elements.

LIFO Operations

Last element inserted is the first to be removed, ensuring ordered access.

Dynamic Size

Can be implemented with fixed arrays or dynamic linked lists.

Types of Stack Implementation

Fixed Size Stack

Array-based implementation with predetermined maximum capacity.

Characteristics:

  • Size defined at creation time
  • Cannot exceed predefined capacity
  • Memory allocated upfront

Advantages:

  • Simple to implement
  • Efficient when maximum size is known
  • Fast access due to contiguous memory

Disadvantages:

  • Memory wastage if not fully utilized
  • Stack overflow if capacity exceeded
  • Difficult to resize dynamically

Dynamic Size Stack

Linked list-based implementation that grows and shrinks as needed.

Characteristics:

  • Grows/shrinks based on usage
  • Memory allocated on demand
  • No predefined size limit

Advantages:

  • No memory wastage
  • Handles unexpected growth
  • Flexible size management

Disadvantages:

  • Slightly more complex implementation
  • Additional memory overhead for pointers
  • Non-contiguous memory allocation

Learning Path

Understand LIFO Principle - Master the core concept with real-world examples

Learn Basic Operations - Study push, pop, peek, and isEmpty operations

Compare Implementations - Understand array vs linked list trade-offs

Practice Applications - Explore use cases like expression evaluation and function calls

Next Steps

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