LeetCode --- Add Two Numbers

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

My Submitted Code

/**
* 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=NULL;
ListNode* tail=NULL;
ListNode* p1=l1;
ListNode* p2=l2;
list<int> carrs;
while(p1||p2){
int carry=0;
if (!carrs.empty())
{
carrs.pop_back();
carry=1;
}
int sum=0;
if(p1){
sum+=p1->val;
}
if(p2){
sum+=p2->val;
}
sum+=carry;
if(sum>=10){
carrs.push_back(1);
}
ListNode* node=new ListNode(sum%10);
if(!head){
head=node;
tail=node;
}else{
tail->next=node;
tail=node;
}
if(p1){
p1=p1->next;
}
if(p2){
p2=p2->next;
}

}
if(!carrs.empty()){
ListNode* node=new ListNode(1);
tail->next=node;
}
return head;
}
};