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

/**
 * 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) {
       int In=0;
       ListNode *pHead=new ListNode(0);
       ListNode *p=pHead;
    
       while(l1!=NULL||l2!=NULL)
       {
           int temp1=0;
           if(l1!=NULL)
           {
               temp1=l1->val;
               l1=l1->next;
           }
           
           int temp2=0;
           if(l2!=NULL)
           {
               temp2=l2->val;
               l2=l2->next;
           }
           
           int temp=temp1+temp2+In;
           p->next=new ListNode(temp%10);
           In=temp/10;
           
           p=p->next;
       }
       
       if(In==1)
       p->next=new ListNode(1);
       
       return pHead->next;
    }   
};

LeeCode---Add Two Numbers