Multiply 2 LL

class Solution {
public:
ListNode *rev(ListNode *head){
    if (head->next==NULL)
    {
        return head;
    }
    ListNode *small=rev(head->next);
    head->next->next=head;
    head->next=NULL;
    return small;   
    }
ListNode* addTwoNumbers(ListNode* l1, ListNode* l2) {
if(!l1||!l2){
return NULL;}
if(l1->val==0 || l2->vl==0){
ListNode* head=new ListNode(0);
return head;
}
        l1=rev(l1);
        l2=rev(l2);
        int carry=0;
ListNode* tail=NULL;
    ListNode* head=NULL;
    int second=0;
    int i=1;
    while(l2){
        second=second+(l2->val*i);
        i=i*10;
        l2=l2->next;
    }
    cout<<second;
    while(l1||carry){
        ListNode* temp;
        int sum=(((l1?l1->val:0)*(second))+carry);
        temp=new ListNode(sum%10);
        carry=sum/10;
        if(head==NULL){
            head=temp;
            tail=temp;
        }
        else{
            tail->next=temp;
            tail=tail->next;
        }
        l1=l1?l1->next:l1;
    }
    return rev(head);
        
    }
};