Tree Traversal Pseudocode PQ

Duration: 7 min

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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.

The video lecture analyzes a recursive C function named `what` designed to traverse a binary tree. The instructor begins by displaying the code, which contains three `printf` statements and two recursive calls to `what` for the left and right children. He draws a sample binary tree on the whiteboard with a root node of value 1, a left child 2 (which has a left child 4), and a right child 3. The instructor then performs a step-by-step trace of the function execution. He demonstrates that for every node visited, the data is printed three times: once before the left child recursion, once between the left and right child recursions, and once after the right child recursion. By following the call stack, he derives the final output sequence: 1 2 4 4 4 2 2 1 3 3 3 1. The lesson emphasizes understanding the order of operations in recursive tree traversals.

Chapters

  1. 0:00 – 2:00 00:00-02:00

    The video opens with the code snippet for the function `void what(struct Bnode *t)`. The instructor introduces the problem of determining the function's behavior. He draws a binary tree on the right side of the screen, starting with a root node labeled 1. He adds a left child labeled 2 and a right child labeled 3. He further extends the tree by adding a left child labeled 4 to node 2. The instructor begins tracing the function by writing `what(1)` on the board, indicating the initial call with the root node. He underlines the first line of code inside the `if (t)` block, which is `printf("%d', t->data);`, explaining that this will print the data of the current node.

  2. 2:00 – 5:00 02:00-05:00

    The instructor continues the trace by underlining the next line, `what(t->LC);`, which represents a recursive call to the left child. He writes `what(2)` below `what(1)` to show the next step in the recursion. Inside the call for node 2, he explains that the data 2 is printed first. Then, the function calls `what(t->LC)` again, moving to node 4. For node 4, the data 4 is printed. Since node 4 has no left child, `what(NULL)` is called and returns immediately. The function then prints 4 again (the second `printf`), calls `what(t->RC)` (which is NULL and returns), and finally prints 4 a third time. The instructor writes the sequence `4 4 4` on the board to represent the output for node 4. Back in node 2, after the left child returns, the second `printf` prints 2 again. The right child call is NULL, so it returns, and the final `printf` prints 2 a third time.

  3. 5:00 – 7:17 05:00-07:17

    The trace returns to the root node 1. After the left subtree (node 2) finishes, the second `printf` in the root function executes, printing 1 again. Next, the function calls `what(t->RC)`, moving to the right child, node 3. The instructor explains that node 3 follows the same pattern: print 3, call left (NULL), print 3, call right (NULL), print 3. This results in the sequence `3 3 3`. Finally, the function returns to the root node 1 one last time, where the final `printf` statement executes, printing 1 for the third time. The instructor writes the complete output sequence on the board: `1 2 4 4 4 2 2 1 3 3 3 1`. He concludes by summarizing that the function prints each node's data three times in a specific order: pre-order, in-order, and post-order relative to the recursive calls.

The lecture provides a clear, visual method for tracing recursive functions on binary trees. By breaking down the code into its constituent parts—printing data and making recursive calls—the instructor shows how the execution flow determines the output. The key learning point is that the position of `printf` statements relative to the recursive calls dictates the traversal order. In this specific case, the function performs a custom traversal where every node is visited and printed three times: before descending left, between left and right descents, and after descending right. This reinforces the concept that recursive functions execute code sequentially, and the 'return' from a recursive call resumes execution at the line immediately following the call.

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