leetcode记录-Add Two Numbers

You are given two linked lists representing two non-negative numbers. 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.

Input: (2 -> 4 -> 3) + (5 -> 6 -> 4)
Output: 7 -> 0 -> 8

class Solution {public:    ListNode *addTwoNumbers(ListNode *l1, ListNode *l2) {        int sum = 0;        int carry = 0;        ListNode* head = new ListNode(-1);        ListNode* p = head;        while(l1 || l2)        {            if(l1 && l2)            {                sum = l1->val + l2->val + carry;            }            else if(l1)            {                sum = l1->val + carry;            }            else            {                sum = l2->val + carry;            }                        if(sum>9)            {                sum-=10;                carry = 1;            }            else            {                carry = 0;            }                        ListNode* node = new ListNode(sum);            p->next = node;            p = node;                        if(l1)            {                l1 = l1->next;            }            if(l2)            {                l2 = l2->next;            }        }                if(carry == 1)        {            ListNode* node = new ListNode(1);            p->next = node;            p = node;        }        p->next = NULL;                return head->next;    }};