Master essential data structures and algorithms: linked lists, stacks, queues, graphs, trees, heaps, and hashing.

Computer Science Bootcamp

Data structures are used to store and manipulate data efficiently. Learning data structures is essential as it enables us to design optimal algorithms and enhances problem-solving capabilities. This module covers the essential data structures and algorithms. We’ll start by understanding commonly used data structures like linked lists, stacks, queues, graphs, trees, heaps, and hashing. Then, we’ll explore various operations and challenges, from insertion and deletion to searching and traversal. By the end of this module, we’ll be equipped to solve complex problems, improve code efficiency, and enhance our career prospects in the ever-growing tech industry.

Data Structures in Python

# Statement

Given the `head` of a singly linked list, reverse the linked list and return its updated `head`.

**Constraints:**

Let `n` be the number of nodes in a linked list.

* $1 \leq$ `n` $\leq 5\times10^2$
* $-5\times10^3 \leq$ `Node.value` $\leq 5\times10^3$

# Solution
We will reverse the linked list without using any additional data structures by keeping track of the current, next, and previous nodes. By maintaining references to these nodes, we can iteratively traverse the linked list, updating the references as needed to reverse the order of the elements. This approach ensures that each node’s reference is correctly adjusted to point to its previous node, effectively reversing the linked list.



To reverse the linked list, we will follow these steps:

1. Initialize three pointers: `previous`, `next_node`, and `current`. The `previous` and `next_node` pointers are initialized as NULL, while the `current` pointer is initialized to the head of the linked list. 
2. Iterate over the linked list. While iterating, perform the following steps:
   -   Before changing the `next` pointer of `current`, store the next node in `next_node` to prevent losing the reference to the rest of the list.
   -    Update the `next` pointer of `current` to point to the `previous` node. This effectively reverses the pointer of the current node.
   -    Move `previous` to `current` and `current` to `next_node` to move to the next iteration.

3. After reversing the whole linked list, we’ll change the head pointer to the `previous` pointer because `previous` will be pointing to the new head node.

Let’s look at the following illustration to get a better understanding of reversing the linked list:

Let’s solve the Reverse Linked List problem.

Introduction to Linked Lists

Introduction to Stacks and Queues

Introduction to Graphs

Introduction to Trees

Introduction to Heap

Introduction to Hashing

Summary of Data Structures

Conclusion

Solution: Reverse a Linked List

Statement