[LeetCode] Add Two Sum

链表头————–>链表尾
头的数相加，向尾部进位，
注意判断最后一个是否进位

“`
/**
* 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 *p1 = l1;
ListNode *p2 = l2;
ListNode *Head= NULL;
ListNode *Tail= NULL;
//ListNode Tail= (ListNode)malloc(sizeof(ListNode));
int i = 0;
int jinwei =0;
int val1 = 0;
int val2 = 0;
for(;p1!= NULL||p2!= NULL;++i){
if(p1!=NULL){
val1 = p1->val;
p1 = p1->next;
}
else
val1 = 0;

        if(p2!=NULL){            val2 = p2->val;            p2 = p2->next;        }        else            val2 = 0;        ListNode *p = new ListNode((val1+val2+jinwei)%10);        jinwei = (val1+val2+jinwei)/10;        if(Head == NULL)            Head = p;        else            Tail->next = p;        Tail = p;    }    if(jinwei){        ListNode *p = new ListNode(jinwei);        Tail->next = p;    }    return Head;}

};“`