Stack Practice questions

Duration: 7 min

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Inside: a video lesson and guided study material.

Module outline

  1. About the course: About the Course
  2. Mathematical Aptitude: Number System, HCF LCM, Divisibility Rules, Percentage, Ratio and Proportion (Ratios), Average, Profit and Loss, Time and Work, Mensuration and Geometry, Simple Interest and Compound Interest, Speed Time and Distance, Age Problems, Mixture and Alligation, Algebra, Powers and Exponents (Surds and Indices), Pipe and Cistern, Trigonometry, Statistics, Data Interpretation, Arithmetic
  3. Logical Reasoning: Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Analogy, Blood Relations, Directions (Direction Test), Ranking, Order and Sequence, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Seating Arrangements, Syllogisms, Venn Diagram, Puzzle Solving (Puzzles), Logical Sequence Of Words, Deductive and Inductive Reasoning (Logical Deduction and Induction) (Prepositional Reasoning), Analytical Reasoning (Counting Figures Reasoning), Cubes & Dices, Calendar, Clock
  4. General Knowledge: Physics, Chemistry, Biology, History, Geography, Polity, Indian Economy, GK- Current Affairs, Static General Knowledge
  5. Art of Teaching: Nature, Objectives & Characteristics of Teaching, Learners & Learning Process, Factors Affecting Teaching, Methods of Teaching, Classroom Management & Communication, Teaching-Learning Aids & ICT Integration, Evaluation, Assessment & Measurement, Professional Development & Ethics, Policies, Acts & Contemporary Issues, Curriculum & School Environment, Guidance, Counselling & Mental Health, Inclusive Education & Special Needs, Micro-Teaching & Teaching Skills, Lesson Planning
  6. Environmental Science: Environment
  7. Unit 1 | Digital Electronics: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  8. Unit 2 | COA: Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Instr Formats & Modes, Control Unit Design, Register Transfer and Microoperations, Programming the Basic Computer
  9. Unit 3 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  10. Unit 3 | Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing
  11. Unit 4 | Algorithms: Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Dynamic Programming, Minimum Spanning Trees, Shortest Path Algos, Advanced Algorithms
  12. Unit 5 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Threads & Process Creation, Deadlock, Memory Management, Virtual Memory, Disc Scheduling, File Management
  13. Unit 6 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, File Organization & Indexing, Relational Algebra, SQL, Transaction Management, Concurrency Control
  14. Unit 7 | Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, DLL: Framing, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Net Layer:Routing Protocol, Transport Layer Services, TL: Congestion & UDP, Application Layer
  15. Unit 8 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  16. Unit 9 | Object Oriented Programming: OOPS with C++
  17. Unit 10 | Web Development: HTML Basics, CSS, JavaScript-Basics, XML
  18. Unit 11 | Theory Of Computation: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines
  19. Unit 12 | IoT: Emerging Tech Trends, Cloud Computing
  20. Unit 13 | Artificial Intelligence: Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Natural Language Processing, Artificial Neural Networks, Genetic Algorithms
  21. Unit 14 | E-Commerce: Electronic Data Interchange and E-Commerce, Role of Internet and Web Services, Security in Mobile and Wireless Computing, Physical Security and Cryptography Basics, Cyber Safety and Security
  22. Unit 15 | Multimedia: Multimedia
  23. Unit 16 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis, DSA using Python
  24. Full Length Mock Tests — General Paper:
  25. Full Length Mock Tests — Computer Science (Paper II):
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

The video presents a computer science problem asking to identify the functionality of a specific C function named `fun`. The instructor systematically analyzes the code by tracing its execution with a concrete example, `n = 81`. He explains the recursive logic where the function divides the input by 3 repeatedly. The core concept is determining whether a number is a power of 3 based on its divisibility properties. The instructor contrasts a valid case (81) with an invalid case (21) to verify the function's behavior against the provided multiple-choice options. The lesson emphasizes understanding base cases and recursive steps in algorithm analysis.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The session begins with the instructor writing `n = 81` on the whiteboard to serve as a test input. He notes that 81 is a multiple of 3 ($3 imes 27$). He starts the trace for `fun(81)`. The first condition `if (n == 0 || n == 1)` evaluates to false. The second condition `if (n % 3 != 0)` is also false because 81 is perfectly divisible by 3. Consequently, the code executes `return fun(n/3)`, which translates to a recursive call `fun(27)`. He writes `fun(81) -> fun(27)` on the board to visualize the call stack. He highlights that the function keeps dividing by 3 as long as the remainder is zero.

  2. 2:00 – 5:00 02:00-05:00

    The instructor continues the trace for `fun(27)`. He writes `27 % 3 = 0` and `27/3 = 9`, leading to `fun(9)`. The process repeats: `fun(9)` calls `fun(3)`, and `fun(3)` calls `fun(1)`. Upon reaching `n = 1`, the base case `if (n == 0 || n == 1)` becomes true, and the function returns `1`. To ensure this isn't a coincidence, he tests `n = 21`. `21 % 3 = 0` leads to `fun(7)`. Since `7 % 3` is not 0, the function returns `0`. This confirms the function returns 1 for powers of 3 and 0 otherwise. He writes `21/3 = 7` and `7 % 3 = 1` to show the failure point where the condition `if (n % 3 != 0)` becomes true.

  3. 5:00 – 7:20 05:00-07:20

    The instructor summarizes the findings by drawing a visual chain: $81 ightarrow 27 ightarrow 9 ightarrow 3 ightarrow 1$. He explicitly writes $3^4 = 81$ to reinforce that 81 is a power of 3. He reviews the options: (A) claims it returns 1 for multiples of 3, which is incorrect because 21 is a multiple but returns 0. (C) and (D) are also incorrect based on the return values. He selects option (B): "It returns 1 when n is a power of 3, otherwise returns 0". He crosses out the incorrect options to finalize the answer. He emphasizes that the function essentially checks if the number can be reduced to 1 by repeated division by 3, which is the definition of a power of 3.

The lecture provides a clear methodology for debugging recursive functions. By manually stepping through the recursion stack with specific inputs, the instructor deduces the mathematical property the code implements. The distinction between "multiple of 3" and "power of 3" is the key takeaway, demonstrated through the contrasting traces of 81 and 21. The visual aids, such as the call chain and the modulo calculations, are crucial for understanding the flow. The final conclusion solidifies the relationship between the code logic and the mathematical concept of powers.

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