Stack Practice questions

Duration: 7 min

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Inside: a video lesson and guided study material.

Module outline

  1. About Course: About the Course
  2. Paper 1 | General Studies: State Wise GK
  3. Paper 1 | Information and Communication Technology: Role of Internet and Web Services, Security in Mobile and Wireless Computing
  4. Paper 1 | Current Affairs: GK- Current Affairs
  5. Paper 2 | Discrete Mathematical Structure: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Set Theory, Relations, Functions, Graph Theory, Group Theory, Propositional and Predicate Logic, Probability
  6. Paper 2 | Digital Computer Organization And Architecture: Number System, Number Representation, Sequential Circuits, Combinational Circuit, Basics of COA, Floating Point Rep, Cache Memory Organization, Input Output Organisation, Pipelining, Instr Formats & Modes, Register Transfer and Microoperations, Control Unit Design, Programming the Basic Computer
  7. Paper 2 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  8. Paper 2 | Programming Languages & Object-Oriented Programming Concepts: Java, OOPS with C++, Java Fundamentals, Array, String, IO & References
  9. Paper 2 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis
  10. Paper 2 | Data Structure And Algorithms: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Minimum Spanning Trees, Advanced Algorithms
  11. Paper 2 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Process Synchronization, Deadlock, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Unix OS
  12. Paper 2 | 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, Complexity Theory
  13. Paper 2 | Compiler Design: Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization, Run Time Environment
  14. Paper 2 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, Relational Algebra, SQL, Transaction Management, Concurrency Control, Database Recovery, Database Security & Authorization, Enhanced Data Models
  15. Paper 2 | Computer Network And Information Security: Introduction to CN, Data Communication, Application Layer, Hardware basics, Cyber Threats and Malware Attacks, Network Security, 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
  16. Paper 2 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Testing, Software Maintenance and Configuration Management
  17. Paper 2 | Current Trends & Technologies: Emerging Tech Trends, Approaches to AI, Search Algorithms, Game Playing, Knowledge Representation, Planning, Multi Agent Systems, Fuzzy Sets, Natural Language Processing, Artificial Neural Networks, Genetic Algorithms, Artificial Intelligence, Data Warehousing & Mining, Electronic Data Interchange and E-Commerce, Terms & Abbreviations
  18. Paper 2 | Full Length Mock Tests:
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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