https://leetcode.com/problems/add-two-numbers

class Solution {
public:
    ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {

        ListNode* current1 = l1;
        ListNode* current2 = l2;
        ListNode* last=NULL;
        ListNode* result=NULL;

        int d1 = 0;
        int d2 = 0;

        int sum = 0;
        int rem = 0;

        while(current1 != NULL || current2 != NULL){

            if(current1 != NULL){
                d1 = current1->val;

                current1 = current1->next;
            }else{
                d1 = 0;
            }

            if(current2 != NULL){
                d2 = current2->val;

                current2 = current2->next;
            }else{
                d2 = 0;
            }

            sum = (d1+d2) + rem;

            rem = sum / 10;


            ListNode* temp = new ListNode((sum%10),NULL);

            if(result == NULL){
                result = temp;

            }else{
                last->next = temp;
            }

            last = temp;


        }

        if(rem > 0){
            ListNode* temp = new ListNode(rem,NULL);
            last->next = temp;
        }
        return result;

    }
};