Add Two Numbers.java

/**
 * Definition for singly-linked list.
 * public class ListNode {
 *     int val;
 *     ListNode next;
 *     ListNode(int x) { val = x; }
 * }
 */
class Solution {
    public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
        ListNode root = new ListNode(0);
        ListNode node = root;
        int forward = 0;
        while(l1 != null || l2 != null) {
            int value = forward;
            if(l1 != null) {
                value += l1.val;
                l1 = l1.next;
            }
            if(l2 != null) {
                value += l2.val;
                l2 = l2.next;
            }
            node.next = new ListNode(value%10);
            forward = value/10;
            node = node.next;
        }
        if(forward != 0) {
            node.next = new ListNode(forward);
        }
        return root.next;
    }
}