Tree traversal Pseudocode (Inorder)
Duration: 10 min
This video lesson is available to enrolled students.
AI Summary
An AI-generated summary of this video lecture.
The video lecture explains how to determine the output of a recursive C function named `what` that operates on a binary tree. The instructor analyzes the code structure, specifically the recursive calls to left and right children and the print statement in between. He draws a sample binary tree with nodes A, B, C, D, and E to demonstrate the execution. By tracing the function call stack step-by-step, he shows that the function performs an in-order traversal, printing the nodes in the sequence D, B, E, A, C.
Chapters
0:00 – 2:00 00:00-02:00
The video begins with a slide displaying the question 'Find what this function is doing?' alongside a C code snippet `void what(struct Bnode *t)`. The instructor underlines `struct Bnode *t` to identify the data structure. He explains the `if (t)` condition which serves as a base case. To illustrate, he draws a binary tree on the right side of the screen, starting with a root node 'A', adding left child 'B' and right child 'C', and then adding children 'D' and 'E' to node 'B'.
2:00 – 5:00 02:00-05:00
The instructor begins tracing the function execution using a stack diagram. He draws a stack frame for the root node 'A' at address 1000, labeling fields 'LC', 'Data', and 'RC'. He explains that the first line `what(t -> LC)` triggers a recursive call to the left child 'B' at address 2000. He draws a new stack frame for B and continues the recursion to node 'D' at address 4000, writing `w(1000)`, `w(2000)`, and `w(4000)` to track the call stack depth.
5:00 – 10:00 05:00-10:00
The trace reaches the leaf node D. The instructor notes that D's left child is null, so the recursive call returns immediately. The `printf` statement executes, printing 'D'. He writes 'D' on the board. Control returns to B, where `printf` prints 'B'. Then, the function calls `what(t -> RC)` for B, moving to node E at address 5000. He traces E: left child null, print E, right child null. Control returns to A, `printf` prints 'A'. Finally, `what(t -> RC)` for A moves to node C at address 3000, which is traced similarly.
10:00 – 10:01 10:00-10:01
The video concludes with the final result. The instructor writes the sequence of printed values 'D B E A C' in a box at the bottom left. He explains that this specific order—Left subtree, Root, Right subtree—defines an in-order traversal. The final output is highlighted to confirm the function's behavior.
The lecture demonstrates a systematic approach to tracing recursive functions on tree data structures. By visualizing the call stack and following the order of operations (Left, Root, Right), the instructor proves that the function performs an in-order traversal. This method is essential for understanding recursion and tree algorithms in computer science.