DSA Stacks - Practice Questions 2026
Course Overview
About This Free Course
Mastering Data Structures and Algorithms (DSA) is the cornerstone of passing technical interviews at top-tier tech companies. Among these structures, the Stack is perhaps the most fundamental yet versatile tool in a programmer's arsenal. This Udemy course is meticulously designed to transform your understanding of Stacks from basic theory to advanced, interview-ready mastery.
Why Serious Learners Choose These learn aws certified ai practitioner aif c01 practice exams 2026
Aspiring software engineers choose these practice exams because they bridge the gap between "knowing" what a stack is and "applying" it under pressure. Unlike standard tutorials, these exams challenge your ability to recognize patterns like Last-In-First-Out (LIFO), handle edge cases, and optimize space-time complexity. We focus on conceptual depth, ensuring you don't just memorize solutions but understand the underlying logic required for FAANG-level interviews.
Course Structure
Our curriculum is divided into six strategic levels to ensure a smooth but rigorous learning curve:
Basics / Foundations: Start with the absolute essentials. This section covers the definition of a stack, LIFO principles, and basic operations like Push, Pop, Peek, and IsEmpty. It ensures you have the vocabulary and mental model needed for more complex tasks.
Core Concepts: Move into gen ai readiness implementation and transformation details. You will be tested on how stacks function using different underlying structures such as arrays and linked lists, including the pros and cons of each approach regarding memory allocation.
Intermediate Concepts: Here, we dive into classic algorithmic problems. You will encounter questions regarding expression parsing, such as converting Infix to Postfix and Prefix notations, as well as balancing parentheses in strings.
Advanced Concepts: Challenge yourself with complex stack-based optimizations. This includes the Monotonic Stack pattern, finding the Next Greater Element, and calculating the Largest Rectangle in a Histogram.
Real-world Scenarios: Understand how stacks power the technology we use daily. This section covers browser history (back/forward functionality), undo/redo mechanisms in editors, and function call stack management in recursion.
Mixed Revision / Final Test: A comprehensive simulation of a real coding interview. These questions are randomized across all difficulty levels to test your agility and retention under a timed environment.
Question 1
What is the time complexity of the "Pop" operation in a stack implemented using a singly linked list, assuming you have a pointer to the head?
Option 1: O(n)
Option 2: O(log n)
Option 3: O(1)
Option 4: O(n log n)
Option 5: O(n^2)
CORRECT ANSWER: Option 3
CORRECT ANSWER EXPLANATION:
In a linked list implementation of a stack, the "top" of the stack is represented by the head of the list. Popping an element involves removing the head node and updating the head pointer to the next node. Since this operation does not depend on the number of elements in the stack, it is performed in constant time, O(1).
WRONG ANSWERS EXPLANATION:
Option 1: O(n) is incorrect because we do not need to traverse the entire list to remove the first element.
Option 2: O(log n) usually refers to tree-based operations and is not applicable to simple linked list head removal.
Option 4: O(n log n) is a complexity associated with sorting algorithms, not basic stack operations.
Option 5: O(n^2) represents quadratic time, which would be extremely inefficient for a basic data structure operation.
Question 2
Which of the following stack applications is used to evaluate a Postfix expression (Reverse Polish Notation)?
Option 1: Breadth-First Search
Option 2: Operand Stack
Option 3: Priority Queueing
Option 4: Binary Search
Option 5: Selection Sort
CORRECT ANSWER: Option 2
CORRECT ANSWER EXPLANATION:
When evaluating a Postfix expression, we use a stack to store operands. When an operator is encountered, we pop the required number of operands (usually two), perform the operation, and push the result back onto the stack.
WRONG ANSWERS EXPLANATION:
Option 1: Breadth-First Search (BFS) utilizes a Queue, not a Stack.
Option 3: Priority Queueing is used for element ordering based on importance, not for linear expression evaluation.
Option 4: Binary Search is a searching algorithm for sorted arrays and does not involve postfix evaluation logic.
Option 5: Selection Sort is a comparison-based sorting algorithm and is unrelated to expression parsing.
Question 3
In a fixed-size array implementation of a stack, what condition occurs when you try to "Push" an element onto a stack that is already full?
Option 1: Underflow
Option 2: NullPointerException
Option 3: Memory Leak
Option 4: Overflow
Option 5: Garbage Collection
CORRECT ANSWER: Option 4
CORRECT ANSWER EXPLANATION:
Stack Overflow occurs when the stack has reached its maximum capacity (defined by the array size) and an attempt is made to add another element. This is a common error in static memory allocation.
WRONG ANSWERS EXPLANATION:
Option 1: Underflow occurs when you try to "Pop" from an empty stack, not "Push" to a full one.
Option 2: While a NullPointerException might occur in some languages if the array isn't initialized, the logical state of a full stack is defined as Overflow.
Option 3: A Memory Leak involves failing to release memory that is no longer needed; it is not the result of pushing to a full stack.
Option 5: Garbage Collection is the process of reclaiming memory from objects no longer in use and is not a stack state condition.
Course Features and Benefits
Welcome to the best practice exams to help you prepare for your DSA Stacks. This course is designed to provide a comprehensive and interactive learning experience.
Unlimited Retakes: You can retake the exams as many times as you want to ensure you have mastered every concept.
Original Question Bank: This is a huge original question bank designed by experts, not just a collection of common internet questions.
Instructor Support: You get support from instructors if you have questions or need clarification on specific logic.
In-depth Feedback: Each question has a detailed explanation to help you understand the "why" behind the correct answer.
Mobile Access: This course is fully mobile-compatible with the Udemy app, allowing you to practice on the go.
Risk-Free: We offer a 30-days money-back guarantee if you're not satisfied with the quality of the practice exams.
We hope that by now you're convinced! And there are a lot more questions inside the course to help you ace your next interview.
Who Should Take This Course
"DSA Stacks - Practice Questions 2026" is aimed at people who want a practical, structured introduction to development without paying full price for it. It's a solid fit if you're starting out in development and want a guided course rather than piecing tutorials together yourself, if you've tried free YouTube content on the topic and want something more organized, or if you already work in a related area and want a refresher you can finish at your own pace. Since enrollment happens on Udemy itself, you keep full access to view the lectures, download any provided resources, and revisit the material later — this isn't a stripped-down or time-limited version of the course.
Why This Course Is Worth Taking
Our take: this listing earns a spot on FreeWebCart because the coupon we verified actually brings the price to $0, not just a token discount, and the course carries a 4.5/5 rating on Udemy. That combination — real reviews plus a working 100% OFF code — is what we look for before publishing a development course. It won't replace hands-on experience or a full degree program, but as a low-risk way to test whether development is worth pursuing further, or to pick up one specific skill, the free price tag makes it an easy yes while the coupon lasts.
Pros & Cons
👍 Pros
- 100% free to enroll via this coupon (normally $19.99)
- Lifetime access on Udemy once enrolled, even after the coupon expires
- Rated 4.5/5 by past students on Udemy
- Self-paced — no fixed schedule or live sessions to attend
👎 Cons
- Coupon is time-limited and can expire before you enroll
- No live instructor support — questions go through Udemy's Q&A, not us
- Certificate is a Udemy completion certificate, not an accredited qualification
Frequently Asked Questions
Is "DSA Stacks - Practice Questions 2026" really free?
Yes — we verified a 100% OFF Udemy coupon for this development course before publishing it. Enroll directly on Udemy using the button below; no credit card is needed while the coupon is active.
How long will this coupon last?
Udemy coupons typically last 1–3 days or expire after roughly 1,000 enrollments, whichever comes first. If the price on Udemy no longer shows $0 when you click through, the coupon has expired since we last checked it.
Do I keep access after the coupon expires?
Yes. Once you enroll while the coupon is live, "DSA Stacks - Practice Questions 2026" is yours to keep on Udemy — including any future updates the instructor makes — even after the coupon runs out.
Save $19.99 - Limited time offer
More Free Development Courses
AWS Certified AI Practitioner (AIF-C01) Practice Exams 2026
The Complete Guide to Negotiation: Tools and Strategies
Learn React: Build Stopwatch Project
