23 Jan - DS - Linked List Practice + Trees
Duration: 1 hr 26 min
This video lesson is available to enrolled students.
AI Summary
An AI-generated summary of this video lecture.
This video is a comprehensive lecture on data structures, focusing on linked lists and binary trees. The session begins with a review of fundamental linked list operations, including recursive search, insertion at the start and after a location, deletion from the start and after a location, and reversing a list, with the instructor providing C-style pseudocode and visual diagrams for each. The lecture then transitions to a series of multiple-choice questions that test conceptual understanding of linked list properties, such as time complexity, memory access, and the effects of pointer manipulation. The final segment introduces binary trees, covering their classification into strict and complete trees, and defining key properties like degree, height, and the relationship between internal nodes and total nodes.
Chapters
0:00 – 2:00 00:00-02:00
The video opens with a title slide for "Session-7" by "Ekagra Sir". The instructor, a man in a black polo shirt, appears in a small window in the top right corner. The main screen is initially black, then transitions to the title slide, which remains for the duration of this segment.
2:00 – 5:00 02:00-05:00
The instructor presents a question to write C-style pseudocode for a recursive search in a linked list. The code for the `Node* Search(Node *ptr, int key)` function is displayed, including the base case `if(ptr == NULL)` and the recursive case `return search(ptr->next, key);`. The instructor explains the logic, highlighting the exit conditions for not found and found.
5:00 – 10:00 05:00-10:00
The lecture moves to a question on inserting a node at the start of a linked list. The code for `Node* CreateNewNode(int key)` and `void Insert(Node** head, int key)` is shown. The instructor uses a diagram to illustrate the process, showing the new node being created and its `next` pointer being set to the current head, followed by updating the head pointer to point to the new node.
10:00 – 15:00 10:00-15:00
The instructor presents a question on inserting a node after a given location. The code for `void InsertAfter(Node* loc, int key)` is displayed. The diagram shows the new node being created, its `next` pointer being set to the node after the location, and the `next` pointer of the location node being updated to point to the new node.
15:00 – 20:00 15:00-20:00
The topic shifts to deleting a node from the start. The code for `void deleteAtHead(Node** head)` is shown. The instructor explains the process: storing the head node in a temporary pointer, updating the head to point to the next node, and then freeing the memory of the original head node.
20:00 – 25:00 20:00-25:00
The instructor discusses deleting a node after a given location. The code for `void deleteAfter(Node* loc)` is presented. The diagram illustrates the process: the node to be deleted is stored in a temporary pointer, the `next` pointer of the location node is updated to skip the deleted node, and the memory of the deleted node is freed.
25:00 – 30:00 25:00-30:00
The lecture covers reversing a linked list. The code for `void reverse(Node** head)` is shown, using a three-pointer technique (prev, current, next). The instructor explains the loop that iterates through the list, reversing the `next` pointers of each node.
30:00 – 35:00 30:00-35:00
A multiple-choice question is presented about linked list implementation compared to arrays. The options discuss cache locality, ease of insertion/deletion, and random access. The instructor explains that arrays have better cache locality, linked lists are easier to insert/delete, and random access is not allowed in linked lists, making all statements true.
35:00 – 40:00 35:00-40:00
The instructor presents a question about the output of a recursive function `fun` that traverses a linked list. The function prints the data of the current node, then recursively calls itself on the node two steps ahead. The instructor walks through the execution, showing the output is 1, 3, 5, 3, 1.
40:00 – 45:00 40:00-45:00
A question is posed about a function `traverse` that traverses a linked list. The function modifies the `head` pointer. The instructor explains that the function is implemented incorrectly because it changes the head, which is a side effect that could cause issues.
45:00 – 50:00 45:00-50:00
The instructor presents a question about a function `reverse` that reverses a linked list using a double pointer `head_ref`. The code is shown with a missing line at the end. The instructor explains that the missing line must be `*head_ref = prev;` to update the head pointer to the new head of the reversed list.
50:00 – 55:00 50:00-55:00
A multiple-choice question asks which operation's time complexity depends on the length of a linked list when pointers to the first and last elements are available. The options are deleting the first, interchanging the first two, deleting the last, and adding an element at the end. The instructor explains that deleting the last element requires traversing the list, so its time depends on the length.
55:00 – 60:00 55:00-60:00
The instructor presents a question about a sequence of operations on a linked list. The steps are `p = getnode()`, `info(p) = 10`, `next(p) = list`, and `list = p`. The instructor explains that this sequence inserts a new node at the beginning of the list, which is an insertion at the beginning operation.
60:00 – 65:00 60:00-65:00
A question presents four statements about data structures. The instructor evaluates each: (i) Stacks support LIFO, (ii) Lists on stacks are more efficient than on arrays, (iii) Queues on circular arrays are more efficient than on linear arrays, (iv) Queues support FIFO. The instructor marks (i) and (iv) as true, and (ii) and (iii) as false.
65:00 – 70:00 65:00-70:00
Another question asks which operation's time depends on the length of a linked list with F and L pointers. The options are deleting the last, deleting the first, adding after the last, and interchanging the first two. The instructor explains that deleting the last element requires traversing from the front to the second-to-last node, so its time depends on the length.
70:00 – 75:00 70:00-75:00
A question asks about two statements regarding circular lists. (i) Insertion should be at the last node, (ii) Deletion should be at the last node. The instructor explains that insertion at the last node is correct for a circular list, but deletion at the last node is not standard, so the first is true and the second is false.
75:00 – 80:00 75:00-80:00
The instructor presents a question about a function `rearrange` that swaps adjacent nodes in a linked list. The function uses a loop to swap the values of two nodes at a time. The instructor explains that the list will be rearranged to 2, 1, 4, 3, 6, 5, 7.
80:00 – 85:00 80:00-85:00
The instructor presents a question about a function `move_to_front` that moves the last element of a linked list to the front. The code is shown with a missing line. The instructor explains that the missing line must be `head = p;` to update the head pointer to the new first node.
85:00 – 85:58 85:00-85:58
The video transitions to a new topic. A title slide appears with the word "Tree" and the subtitle "Binary Tree Basics & Props". The instructor begins to discuss the classification of trees, starting with the first type, "Strict Tree".
This video provides a comprehensive review of linked list operations and their implementation, followed by a transition into the fundamentals of binary trees. The lecture is structured as a problem-solving session, where the instructor first presents a concept with pseudocode and diagrams, then follows up with multiple-choice questions to test understanding. The core of the linked list section covers the essential operations: search, insert, and delete, both at the beginning and at a specific location, as well as reversing the list. The instructor emphasizes the importance of pointer manipulation and the use of temporary variables. The final segment introduces binary trees, beginning with their classification into strict and complete trees, and defining key properties like degree and height, setting the stage for more advanced topics.