12. Add Two Numbers

class Solution {
	public ListNode addTwoNumbers(ListNode l1, ListNode l2) {
		ListNode dummy = new ListNode(0);
		ListNode p = l1, q = l2, curr = dummy;
		int carry = 0;

		while(p != null || q != null) {
			int x = p!=null ? p.val : 0;
			int y = q!=null ? q.val : 0;
			int sum = x + y + carry;
			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 dummy.next;
	}
}