LeetCode Add Two Numbers

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.

Solution:

class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
        ListNode* dummy = new ListNode(0);
        ListNode* pre = dummy;
        int carry = 0;
        while(l1 || l2 || carry) {
            int tmp = (l1 ? l1->val : 0) + (l2 ? l2->val : 0) + carry;
            pre->next = new ListNode(tmp % 10);
            carry = tmp/10;
            pre = pre->next;
            l1 = l1 ? l1->next: l1;
            l2 = l2 ? l2->next: l2;
        }
        return dummy->next;
    }
};

几种情况合并在一个循环中。