Stack Operations & Application🔗

A stack is a linear data structure that follows the Last-In First-Out (LIFO) principle.

Basic Stack Operations

Application of Stack🔗

Function Call Management
- Every function call is pushed to the call stack and popped when it returns
Expression Evaluation and Conversion
- Infix to Postfix/Prefix Conversion
- Postfix Expression Evaluation
Undo Mechanisms in Editors and Apps
- Each operation is pushed onto a stack, undo just pops the last action
Syntax Parsing
- Used in Compilers to parse Expressions, Match Brackets, and More
Backtracking
- Pathfinding, Maze Solving, Puzzle Solving (DFS uses stack)
Memory Management
- Stacks are use for stack frame in program execution

Python (builtin or collections.deque)

Operation	Using list	Using deque
Create stack	stack = []	`from collections import deque` then `stack = deque()`
Push	stack.append(x)	stack.append(x)
Pop	stack.pop()	stack.pop()
Peek	stack[-1]	stack[-1]
Check empty	not stack	not stack

NOTE: deque is faster and preferred for large-scale stack operations

C++ (std::stack)

Operation	Function	Notes
Create stack	stack s	T is the data type
Push	s.push(x)	Adds x to top
Pop	s.pop()	Removes top element
Peek	s.top()	Returns top without removing
Check empty	s.empty()	Returns true if empty
Size	s.size()	Returns number of elements

To use a different container: stack<int, vector<int>> s; or stack<int, deque<int>> s;