Reversing a Link List using Recursion

Duration: 4 min

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  1. About the course: About the Course
  2. Mathematical Aptitude: संख्या पद्धति / Number System, महत्तम समापवर्तक और लघुत्तम समापवर्त्य / HCF and LCM, Divisibility Rules, प्रतिशत / Percentage, अनुपात और समानुपात / Ratio and Proportion, औसत / Average, लाभ, हानि और बट्टा / Profit, Loss and Discount, समय और कार्य / Time and Work, घन क्षेत्रमिति / Solid Mensuration, साधारण और चक्रवृद्धि ब्याज / Simple and Compound Interest, समय, चाल और दूरी / Time, Speed and Distance, Age Problems, मिश्रण और एलिगेशन / Mixture and Alligation, Algebra, सरलीकरण, घातांक और करणी / Simplification, Indices and Surds, Pipe and Cistern, Trigonometry, Statistics, आँकड़ा निर्वचन / Data Interpretation, Arithmetic, समुच्चय, संबंध, फलन और विविक्त गणित / Sets, Relations, Functions and Discrete Mathematics, संख्या पद्धति और संख्या सिद्धांत / Number Systems and Number Theory, निर्देशांक ज्यामिति, सदिश और त्रिविमीय ज्यामिति / Coordinate Geometry, Vectors and 3D Geometry, बहुपद, समीकरण और सम्मिश्र संख्याएँ / Polynomials, Equations and Complex Numbers
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  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
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  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
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  19. Unit 12 | IoT: Emerging Tech Trends, Cloud Computing, कंप्यूटर नेटवर्क / Computer Networks
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  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
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  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.

This educational video provides a detailed walkthrough of reversing a singly linked list using a recursive algorithm in C. The instructor begins by presenting the code structure, specifically the `main` function calling `reverse(null, head)` and the recursive `reverse` function definition. He explains the two-pointer approach where `previous` and `current` are passed down the recursion stack. The core of the lesson involves a step-by-step trace of the execution on a list containing nodes 'a', 'b', 'c', and 'd', demonstrating how the call stack builds up and then unwinds to update the pointers in reverse order.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The instructor introduces the problem of reversing a linked list and displays the C code on the screen. He highlights the `main` function calling `reverse(null, head)` and the function signature `Void reverse(struct node* previous, current)`. He explains the logic: if `current` is not null, it recursively calls itself with `current` as the new `previous` and `current->next` as the new `current`. The base case is when `current` is null, at which point `Head` is set to `previous`. The instructor begins tracing the execution, writing down the call stack: `reverse(null, 10)`, `reverse(10, 20)`, `reverse(20, 30)`, and `reverse(30, 40)`, representing the addresses of nodes 'a', 'b', 'c', and 'd' respectively.

  2. 2:00 – 3:55 02:00-03:55

    The lecture continues with the base case execution and the unwinding phase. The instructor shows the final recursive call `reverse(40, null)`, where the condition `current != null` fails, triggering the `Else` block to set `Head = 40`. As the recursion returns, the line `Current->link = previous` executes. He traces this specifically: node 'd' (40) points to 'c' (30), node 'c' (30) points to 'b' (20), node 'b' (20) points to 'a' (10), and finally node 'a' (10) points to null. He draws the final state of the linked list on the diagram, showing the arrows reversed from d -> c -> b -> a, confirming the list is now reversed with 'd' as the new head.

The video successfully demystifies recursive linked list reversal by combining code analysis with a visual trace. The instructor effectively uses the call stack diagram to show how the 'previous' pointer accumulates the reversed sequence as the recursion unwinds. By explicitly mapping node addresses (10, 20, 30, 40) to the function arguments, he clarifies how the `Current->link = previous` statement physically reverses the pointers in memory, ensuring students understand both the logical flow and the memory manipulation involved.

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