Leetcode-2 Add Two Numbers

#2.　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

/**
 * 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* head=new ListNode(0);
        ListNode* p=head;
        ListNode* q=head;
        
        int carry=0;
        int sum=0;
        int all=0;
        while(l1!=NULL&&l2!=NULL)
        {
            all=l1->val+l2->val+carry;
            sum=all%10;
            carry=all/10;
            p->val=sum;
            p->next=new ListNode(0);
            p=p->next;
            l1=l1->next;
            l2=l2->next;
        }
        
        while(l1!=NULL)
        {
            all=l1->val+carry;
            sum=all%10;
            carry=all/10;
            p->val=sum;
            p->next=new ListNode(0);
            p=p->next;
            l1=l1->next;
        }
        while(l2!=NULL)
        {
            all=l2->val+carry;
            sum=all%10;
            carry=all/10;
            p->val=sum;
            p->next=new ListNode(0);
            p=p->next;
            l2=l2->next;
        }
        if(carry!=0)
        {
            p->val=1;
            p->next=new ListNode(0);
            p=p->next;
        }
        while(q!=NULL)
        {
            if(q->next->next==NULL)
            {
                q->next=NULL;
                break;
            }
            q=q->next;
        }

        return head;
        
        
    }
};

/**
 * 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* head=new ListNode(0);
        ListNode* p=head;
        
        int carry=0;
        int sum=0;
        int all=0;
        while(l1!=NULL&&l2!=NULL)
        {
            all=l1->val+l2->val+carry;
            sum=all%10;
            carry=all/10;
            p->next=new ListNode(sum);
            p=p->next;
            l1=l1->next;
            l2=l2->next;
        }
        
        while(l1!=NULL)
        {
            all=l1->val+carry;
            sum=all%10;
            carry=all/10;
            p->next=new ListNode(sum);
            p=p->next;
            l1=l1->next;
        }
        while(l2!=NULL)
        {
            all=l2->val+carry;
            sum=all%10;
            carry=all/10;
            p->next=new ListNode(sum);
            p=p->next;
            l2=l2->next;
        }
        if(carry!=0)
        {
            p->next=new ListNode(1);
            p=p->next;
        }
       

        return head->next;
        
        
    }
};