面试题 02.05. 链表求和

https://leetcode-cn.com/problems/sum-lists-lcci/

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution
{
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2)
    {
        ListNode *head = new ListNode(-1), *p1 = l1, *p2 = l2, *p = head;
        int sum = 0, carr = 0;
        while (p1 || p2 || carr) 
        {
            sum = 0;
            if(p1)
            {
                sum += (p1->val);
                p1 = p1->next;
            }
            if(p2)
            {
                sum += (p2->val);
                p2 = p2->next;
            }
            sum += carr; 
            ListNode *t = new ListNode(sum % 10); 
            carr = sum / 10; 
            p->next = t;
            p = p->next;
        }
        return head->next;
    }
};