LeetCode——Add Two Numbers

Question:
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
Solution:

/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     NodeList *next;
 *     NodeList(int x) : val(x), next(NULL) {}
 * };
 */
class Solution {
public:
    ListNode *addTwoNumbers(ListNode *head1, ListNode *head2) {
        int n1=0,n2=0;
    ListNode *ptr1=head1,*ptr2=head2;
    while(ptr1!=NULL)
    {
        n1++;
        ptr1=ptr1->next;
    }
    while(ptr2!=NULL)
    {
        n2++;
        ptr2=ptr2->next;
    }
    vector<int> sum;
    int temp;
    ListNode *head_long,*head_short;
    if(n1>=n2)
    {
        head_long=head1;
        head_short=head2;
    }
    else
    {
        head_long=head2;
        head_short=head1;
    }
    /////
        ListNode *pt1=head_long,*pt2=head_short;
        while(pt2!=NULL)
        {
            temp=pt1->val+pt2->val;
            if(temp>=10)
            {
                sum.push_back(temp%10);
                if(pt1->next==NULL)
                {
                    sum.push_back(1);
                }
                else
                    pt1->next->val+=1;
            }
            else
                sum.push_back(temp);
            pt1=pt1->next;pt2=pt2->next;
        }
        while(pt1!=NULL)
        {
            temp=pt1->val;
            if(temp>=10)
            {
                sum.push_back(temp%10);
                if(pt1->next==NULL)
                {
                    sum.push_back(1);
                }
                else
                    pt1->next->val+=1;
            }
            else
                sum.push_back(temp);
            pt1=pt1->next;
        }
        ListNode *result=new ListNode(0);
        ListNode *rp=new ListNode(0);
        rp=result;
        ListNode *rq;

        for(vector<int>::iterator iter=sum.begin();iter!=sum.end();iter++)
        {
            rq=new ListNode(0);
            rq->val=*iter;
            rp->next=rq;
            rp=rq;
        }

        rp->next=NULL;
        result=result->next;  
        return result;
    }
};