Practice Set 7 (Recursion, Function) Q16-20

Duration: 8 min

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Inside: a video lesson and guided study material.

Module outline

  1. About the Course: About the Course
  2. Section 1 | Language (Hindi): भाषा, लिपि, ध्वनि, वर्ण, अक्षर, स्वर, व्यंजन, मात्रा और संयुक्ताक्षर, वर्तनी, वर्ण-विन्यास, अनुस्वार, अनुनासिक, चंद्रबिंदु और ‘र’ के रूप, शब्द, पद और शब्द-भेद, संज्ञा और सर्वनाम, विशेषण और क्रिया, लिंग, वचन, पुरुष और कारक, काल, वाच्य, वाक्य और वाक्य-भेद, संधि, समास, विलोम शब्द, पर्यायवाची शब्द, सामान्य अशुद्धियाँ, अनेक शब्दों के लिए एक शब्द, मुहावरे और लोकोक्तियाँ, अपठित गद्यांश और अपठित पद्यांश, Multi-Topic Content (Cross-Concept Material), वर्णमाला
  3. Section 1 | Language (उर्दू भाषा — 22 प्रश्न (निश्चित)): Spelling & Diacritics, Grammar (اسم, فعل, صفت, ضمیر), Vocabulary, Idioms & Proverbs, Comprehension
  4. Section 1 | Language (বাংলা / बांग्ला भाषा — 22 प्रश्न (निश्चित)): Bangla Script and Sounds, Bangla Grammar and Usage, Bangla Word Formation and Vocabulary, Reading and Text Interpretation
  5. Section 1 | Language (English): Vocabulary, Noun, Subject Verb Agreement (Verb Noun Agreement), Adjectives, Tenses, Pronoun, Verb, Adverb, Preposition, Articles, Determiner, Conjunction, Modals, Active Passive Voice (Voice), Direct and Indirect Speech, Sentence Correction (Error Correction), Sentence Completion (Fill in the blanks), Sentence Construction, Sentence Re-arrangements (Para Jumbles) (Narrative Sequencing), Comprehension / Reading Comprehension / Unseen Passages (Critical Reasoning) (Paragraph Questions), Cloze Test (Cloze Passage), Verbal Analogy (Word Based Analogy), Facts, Inference and Judgements
  6. Section 2 | Primary Maths & Reasoning: Ratio and Proportion (Ratios), Divisibility Rules, Mixture and Alligation, Permutation and Combination, Number System, HCF LCM, Sequence and Series (Series), Speed Time and Distance, Series (Number and Letter Series) (Numerical Relations and Reasoning), Coding Decoding, Non Verbal Reasoning (Spatial Aptitude) (Spatial Reasoning) (Visual Reasoning), Percentage, Average, Profit and Loss, Simple Interest and Compound Interest, Time and Work, Mensuration and Geometry, Age Problems, Arithmetic, Powers and Exponents (Surds and Indices), Algebra, Probability, Trigonometry, Syllogisms, Seating Arrangements, Blood Relations, Directions (Direction Test), Analytical Reasoning (Counting Figures Reasoning), Puzzle Solving (Puzzles), Calendar, Clock, Cubes & Dices, Venn Diagram, Data Arrangement, Inequality, Analogy, Ranking, Order and Sequence
  7. Section 2 | General Awareness (GK + Current Affairs): Polity, Physics, Biology, State Wise GK, Chemistry, History, Geography, Indian Economy, Environment, GK- Current Affairs, Static General Knowledge
  8. Section 3 | Computer System and Org. (CSO): Basics of COA, Floating Point Rep, Cache Memory Organization, Instr Formats & Modes, Programming the Basic Computer, Input Output Organisation, Register Transfer and Microoperations, Control Unit Design
  9. Section 3 | Database Management System: Basics of DBMS, ER Diagram, Relational Model & Functional Dependencies, Keys & Integrity Constraints, Normalization (1NF - BCNF), Decomposition Properties & 4NF, SQL, File Organization & Indexing, Relational Algebra, Relational Calculus, Transaction Management, Concurrency Control
  10. Section 3 | Operating System: Introduction to OS, Process Management, CPU Scheduling, Threads & Process Creation, Memory Management, Virtual Memory, Disc Scheduling, File Management, Process Synchronization
  11. Section 3 | Computer Networks: Introduction to CN, Data Communication, DLL: Access Control, DLL: Flow Control, DLL: Error Control, Data Link Layer - Ethernet, Net Layer: IPv4 & Proto, Net Layer: IP Addressing, Transport Layer Services, TL: Congestion & UDP, Application Layer, Hardware basics
  12. Section 3 | Data Structures: Introduction to DS, Array, Stack, Queue, Linked List, Tree, Graphs, Hashing, Algorithm Analysis, Time Complexity Analysis, Sorting Algorithms, Greedy Algorithms, Minimum Spanning Trees, Shortest Path Algos
  13. Section 3 | Theory Of Computation & Compiler Design: Introduction to TOC, Deterministic FA (DFA), Non-Deterministic FA, Regular Expressions, Grammar, Regular Language Properties, Moore & Mealy Machines, Pushdown Automata & CFG, Turing Machines, Intro to Compilers, Lexical Analysis, Grammar & CFG, Syntax Analysis: Top-Down, Syntax Analysis: Bottom-Up, Semantic Analysis & SDT, Intermediate Code Gen, Code Optimization
  14. Section 3 | Emerging Trends (AI, Societal Ethics & MS Office): Artificial Intelligence, Emerging Tech Trends, Society, Law & Ethics, MS Office Applications
  15. Section 3 | Software Engineering: Fundamentals of Software Engineering, Software Requirements and Quality Assurance, Software Design, Estimation and Metrics, Software Maintenance and Configuration Management, Software Testing
  16. Section 3 | C Programming: C Fundamentals, Control Flow, Functions, Arrays & Pointers, Storage Classes, Structures & Enums, DMA, Macros, Scoping & File Handling
  17. Section 3 | OOPS, C++, JAVA, HTML: OOPS with C++, Java, HTML Basics, CSS
  18. Section 3 | Java: Java Fundamentals, Array, String, IO & References
  19. Section 3 | Python: Introduction to Python, Tokens, Variables, Data Types, I/O, Operators & Expressions, Control Flow & Looping, Collections & Strings, Functions & Modules, File Handling & Data Analysis
  20. Section 3 | Digital Electronics: Digital Systems & Boolean Basics, Logic Gates & Hardware, Boolean Expression, Boolean Minimization, Combinational Circuit, Sequential Circuits, Number System, Number Representation
  21. Section 3 | Multimedia: Multimedia
  22. BPSC Previous Year Papers:
  23. BPSC Full Mock Tests:
AI summary & chapters

AI Summary

An AI-generated summary of this video lecture.

This video is a lecture on Python programming, focusing on solving a series of practice questions from a document titled 'Python Practice Question Sheet.pdf'. The instructor, a man in a dark blue shirt, uses a digital whiteboard to explain the logic and execution of various Python functions. The session begins with Question 16, which involves a recursive function to calculate the factorial of 6, with the instructor demonstrating the step-by-step recursion process. The video then transitions to Question 17, where the instructor analyzes a function that uses the `isinstance` function to check if an argument is a set, and then calls `len` on it. The final segment covers Question 18 and Question 20, both of which involve recursive functions that manipulate lists. For Question 18, the function `f(n)` returns a list of numbers from n down to 1. For Question 20, the function `f(l, n)` recursively builds a list by taking the first element of the list `l` and appending the result of a recursive call with the rest of the list and a decremented `n`. The instructor uses on-screen diagrams and handwritten calculations to illustrate the recursive calls and their return values, providing a clear, step-by-step walkthrough of each problem.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video starts with Question 16, which presents a recursive function `f(n)` defined as `return 1 if n==0 else n * f(n-1)`. The instructor explains that this is a factorial function and proceeds to calculate `f(6)`. He writes out the recursive expansion on the board: `6 * f(5)`, `5 * f(4)`, and so on, down to `1 * f(0)`. He then calculates the final result as `6 * 5 * 4 * 3 * 2 * 1 = 720`. The on-screen text clearly shows the function definition and the question `print(f(6))`. The instructor uses a yellow marker to draw arrows and write the calculation steps, visually demonstrating the recursion process.

  2. 2:00 – 5:00 02:00-05:00

    The instructor moves to Question 17, which defines a function `f(x)` that checks if `x` is an instance of a set using `isinstance(x, set)`. If true, it returns the length of `x`. The function is then called with `f([1,2,3])`. The instructor explains that a list is not a set, so the condition `isinstance([1,2,3], set)` is false. The function then calls `f(set(x))`, which converts the list to a set `{1,2,3}`. The function is called again with this set, and since `isinstance({1,2,3}, set)` is true, it returns `len({1,2,3})`, which is 3. The instructor writes `f([1,2,3])` and then `f(set([1,2,3]))` on the board, showing the transformation. The on-screen text shows the function definition and the print statement `print(f([1,2,3]))`. The instructor concludes that the output is 3, which corresponds to option (a).

  3. 5:00 – 7:47 05:00-07:47

    The video transitions to Question 18, which defines a function `f(n)` that returns a list. The function returns `[n] + f(n-2)` if `n > 0`, and returns an empty list `[]` if `n == 0`. The instructor demonstrates the recursion for `f(7)`. He writes `f(7)` and then `f(7) = [7] + f(5)`. He continues this process, writing `f(5) = [5] + f(3)`, `f(3) = [3] + f(1)`, and `f(1) = [1] + f(-1)`. Since `n = -1` is not greater than 0, `f(-1)` returns `[]`. The final result is `[7,5,3,1]`. The on-screen text shows the function and the print statement `print(f(7))`. The instructor then moves to Question 20, which defines a function `f(l, n)` that returns a list. The function returns `l[0] + f(l[1:], n-1)` if `n > 0`, and returns `[]` if `n == 0`. The instructor demonstrates `f([1,2,3,4], 2)`. He writes `f([1,2,3,4], 2) = [1] + f([2,3,4], 1)`. Then `f([2,3,4], 1) = [2] + f([3,4], 0)`. Since `n == 0`, `f([3,4], 0)` returns `[]`. The final result is `[1,2]`. The on-screen text shows the function and the print statement `print(f([1,2,3,4], 2))`. The instructor uses the board to draw the recursive calls and their results.

The video provides a comprehensive walkthrough of several Python programming problems, emphasizing the core concept of recursion. The instructor systematically breaks down each question, starting with a clear explanation of the function's logic, followed by a step-by-step trace of the recursive calls. The use of a digital whiteboard to visually map out the recursion tree and calculate intermediate values is a key teaching method. The problems cover different aspects of recursion: calculating a mathematical function (factorial), manipulating data types (converting a list to a set), and building a list from a sequence. The progression from simple mathematical recursion to more complex list manipulation demonstrates a well-structured learning path, helping students understand how to approach and solve recursive problems in Python.

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