source: https://leetcode.com/problems/plus-one-linked-list/description/ Plus One Linked List Given a non-negative integer represented as a linked list of digits, plus one to the integer. The digits are stored such that the most significant digit is at the head of the list. Example 1: Input: head = [1,2,3] Output: [1,2,4] Example 2: Input: head = [0] Output: [1] ...