leetcode 2 Add Two Numbers

/**
 * 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 *newhead=new ListNode(0);
        ListNode *p=newhead;
        int count=0;
        while(l1&&l2)
        {
            
            p->next=new ListNode(0);
            p=p->next;    
            if(l1->val+l2->val+count<=9)
            {    p->val=l1->val+l2->val+count;
                    count=0;
            }
            else
            {p->val=l1->val+l2->val+count-10;
            count=1;
            }
            l1=l1->next;
            l2=l2->next;
        }
        p->next=l1?l1:l2;
        if(count==1)
        {
           if(l1||l2)
            p->next=l1?l1:l2;
            else
            p->next=new ListNode(0);
           while(p->next!=NULL)
            {  p=p->next;
               if(p->val+count<=9)  
               {if(count==1)  
                 p->val+=1;
                 count=0;
               }
                if(p->val+count>9)
                {count=1;
                p->val=0;
                if(p->next==NULL)
                {
                p->next=new ListNode(1);
                count=0;
                }
                }
              
            }
            }
        
        return newhead->next;
    }
};