You are given two non-empty linked lists representing two non-negative integers. The digits are stored in reverse order and each of their nodes contain a single digit. Add the two numbers and return it as a linked list.

You may assume the two numbers do not contain any leading zero, except the number 0 itself.

Example:

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8
Explanation: 342 + 465 = 807.

/**
 * 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 dummyHead = new ListNode(0);
        ListNode p = l1;
        ListNode q = l2;
        ListNode curr = dummyHead;
        
        int carry = 0;
        
        while(p!=null || q!=null){
            int x = (p!=null)?p.val:0;
            int y = (q!=null)?q.val:0;
            int sum = carry+x+y;
            carry = sum/10;
            curr.next = new ListNode(sum%10);
            curr = curr.next;
            if (p!=null) p = p.next;
            if (q!=null) q = q.next;
    
        }
        if(carry>0) {
            curr.next = new ListNode(carry);
        }
        return dummyHead.next;
    }
}

Runtime: 2 ms, faster than 81.17% of Java online submissions for Add Two Numbers.Memory Usage: 44.2 MB, less than 86.83% of Java online submissions for Add Two Numbers.