Given two linked lists, each representing a non-negative integer, add the two numbers and return it as a linked list . For example, given 2->4->3 and 5->6->4, return 7->0->8.

Given an array of integers, find all possible subsets of the array. For example, if the input array is [1, 2, 3], the output should be [], [1], [2], [3], [1,2], [1,3], [2,3], [1,2,3].
Implement a graph data structure in Java and write a method to perform a depth-first search (DFS) starting from a given vertex.
Given two linked lists, each representing a non-negative integer, add the two numbers and return it as a linked list . For example, given 2->4->3 and 5->6->4, return 7->0->8.