Stack 35-47

4.1 Introduction to Stack

A stack is a fundamental linear data structure in computer science, characterized by its Last-In-First-Out (LIFO) principle. This means that the last element added to the stack is the first one to be removed. Stacks are widely used in various applications such as expression evaluation, backtracking algorithms, and function call management in programming languages. The stack is an abstract data type (ADT) that allows two primary operations: push (to insert an element onto the stack) and pop (to remove the topmost element). The stack can be implemented using arrays or linked lists. In a stack, elements are added and removed from only one end, called the 'top' of the stack. This section introduces the concept, importance, and basic operations of stacks, laying the foundation for understanding more advanced stack operations and their applications.

• A stack follows the Last-In-First-Out (LIFO) principle.
• Primary operations are push (insert) and pop (remove).
• Stacks can be implemented using arrays or linked lists.
• The 'top' refers to the end where insertions and deletions occur.
• Stacks are used in expression evaluation and function call management.
• Stack is an abstract data type (ADT).
• 📌 Stack: A linear data structure following LIFO principle.
• 📌 Push: Operation to insert an element onto the stack.
• 📌 Pop: Operation to remove the top element from the stack.

4.2 Stack Operations

Stack operations are the set of actions that can be performed on a stack data structure. The two fundamental operations are push and pop. The push operation adds an element to the top of the stack, while the pop operation removes the top element. Additional operations include peek (or top), which returns the top element without removing it, and isEmpty, which checks if the stack is empty. Another useful operation is isFull, which checks if the stack has reached its maximum capacity (in case of array implementation). Each operation must handle special cases: for example, popping from an empty stack (underflow) or pushing onto a full stack (overflow). Understanding these operations is crucial for implementing stack-based algorithms.

• Push adds an element to the top of the stack.
• Pop removes the top element from the stack.
• Peek returns the top element without removing it.
• isEmpty checks if the stack contains no elements.
• isFull checks if the stack is at maximum capacity.
• Underflow and overflow are important error conditions.
• 📌 Push: Insert operation on stack.
• 📌 Pop: Remove operation from stack.
• 📌 Peek: Retrieve top element without removal.