Stack

Question What is a stack? tap to flip ↻ Answer A linear data structure that follows the Last In, First Out (LIFO) principle. Question What does LIFO stand for? tap to flip ↻ Answer Last In, First Out Question What are the primary operations on a stack? tap to flip ↻ Answer **Push** (insert), **Pop** (remove), **Peek** (access top), and **isEmpty** (check if empty). Question What does the push operation do? tap to flip ↻ Answer Adds an element to the top of the stack. Question What does the pop operation do? tap to flip ↻ Answer Removes and returns the top element of the stack. Question What does the peek operation do? tap to flip ↻ Answer Returns the top element without removing it. Question What is the time complexity of push and pop operations on a stack? tap to flip ↻ Answer $O(1)$ Question What is the space complexity of a stack? tap to flip ↻ Answer $O(n)$ where $n$ is the number of elements in the stack. Question What is a stack overflow? tap to flip ↻ Answer An error that occurs when trying to push an element onto a full stack. Question What is a stack underflow? tap to flip ↻ Answer An error that occurs when trying to pop or peek from an empty stack. Question How can a stack be implemented? tap to flip ↻ Answer Using an **array** or a **linked list**. Question What is the advantage of implementing a stack using a linked list? tap to flip ↻ Answer It can dynamically grow and shrink, avoiding fixed capacity limitations. Question What is the disadvantage of implementing a stack using an array? tap to flip ↻ Answer The stack has a fixed capacity and cannot grow beyond it. Question What is a real-world example of a stack? tap to flip ↻ Answer A stack of plates, where you add and remove plates from the top. Question What is the application of a stack in function calls? tap to flip ↻ Answer The call stack keeps track of function calls and local variables. Question How is a stack used in expression evaluation? tap to flip ↻ Answer Stacks are used to evaluate arithmetic expressions, such as converting infix to postfix and evaluating postfix expressions. Question What is the postfix expression for the infix expression $A + B$? tap to flip ↻ Answer $A B +$ Question How does a stack help in checking balanced parentheses? tap to flip ↻ Answer Push opening parentheses onto the stack; for each closing parenthesis, pop and check if it matches the corresponding opening one. Question What is the top of a stack? tap to flip ↻ Answer The most recently added element that is accessible for pop or peek. Question What is the bottom of a stack? tap to flip ↻ Answer The first element that was pushed onto the stack.