Stacks in Data Structures
A stack is a linear data structure that follows the Last In, First Out (LIFO) principle. The most recently added element is removed first. Stacks are widely used in programming for temporary storage and function management.
What is a Stack?
A stack is a collection of elements with two main operations:
- Push – Add an element to the top
- Pop – Remove the top element
Key Characteristics:
- LIFO structure
- Single access point (top of stack)
- Supports limited operations
Representation of Stack
- Can be implemented using:
- Arrays (static stack)
- Linked lists (dynamic stack)
- Top pointer indicates the current element at the top of the stack.
Basic Operations on Stack
1. Push
Adds an element to the top.
push(element);
2. Pop
Removes the top element.
pop();
3. Peek / Top
Returns the top element without removing it.
peek();
4. isEmpty
Checks if the stack is empty.
isEmpty();
5. isFull
Checks if the stack is full (array implementation).
isFull();
Types of Stacks
1. Static Stack
- Fixed size
- Implemented using arrays
2. Dynamic Stack
- Size can grow
- Implemented using linked lists
Applications of Stack
- Expression evaluation (infix, postfix, prefix)
- Function call management (recursion)
- Undo/Redo operations in text editors
- Browser back/forward navigation
- Syntax parsing in compilers
Advantages of Stack
- Simple to implement
- Efficient memory use
- Useful for recursion and temporary storage
- Easy to maintain order
Disadvantages of Stack
- Fixed size in static implementation
- Access is restricted to top element only
- Not suitable for searching middle elements
Real-World Example of Stack
- Plates in a cafeteria: last plate placed on top is taken first
- Undo feature in Word processors: last change is reverted first
- Browser history: last visited page is accessed first
Stack vs Queue
| Stack | Queue |
|---|---|
| LIFO | FIFO |
| Top element accessed | Front element accessed |
| Push/Pop operations | Enqueue/Dequeue operations |
Conclusion
Stacks are an essential linear data structure used in temporary storage, recursion, and expression evaluation. Understanding stack operations and implementations is vital for solving real-world programming problems and algorithm design.