Leetcode, Add Two Numbers, Programming, Leetcode Medium, Java.
singly-linked list. * public class ListNode { * int val; * ListNode next; * ListNode() {} * ListNode(int val) { this.val = val; } * ListNode(int val, ListNode next) { this.val = val; this.next = next; } * } */ You are given two non-empty linked lists representing two non-negative integers. The