Reverse linked List I and II

The next writting will contain my solution for the following leetcode problems: https://leetcode.com/problems/reverse-linked-list/ and https://leetcode.com/problems/rotate-list/

These two are fairly simple linked list problems. to handle these type of problem is usually recommended to use a dummy node prev that points your current element.

Problem # 206. Reverse Linked List

Given the head of a singly linked list, reverse the list, and return the reversed list.