Linked list written in c++

linked_list.cpp

#include <iostream>
#include <cstdlib>


class Node
{
public:
    Node* next;
    int data;
};

using namespace std;

class LinkedList
{
public:
    int length;
    Node* head;

    LinkedList();
    ~LinkedList();
    void add(int data);
    void print();
};

LinkedList::LinkedList(){
    this->length = 0;
    this->head = NULL;
}

LinkedList::~LinkedList(){
    std::cout << "LIST DELETED";
}

void LinkedList::add(int data){
    Node* node = new Node();
    node->data = data;
    node->next = this->head;
    this->head = node;
    this->length++;
}

void LinkedList::print(){
    Node* head = this->head;
    int i = 1;
    while(head){
        std::cout << i << ": " << head->data << std::endl;
        head = head->next;
        i++;
    }
}

int main(int argc, char const *argv[])
{
    LinkedList* list = new LinkedList();
    for (int i = 0; i < 100; ++i)
    {
        list->add(rand() % 100);
    }
    list->print();
    std::cout << "List Length: " << list->length << std::endl;
    delete list;
    return 0;
}

Can anyone explain me, if we create LinkedtList object then head (wiyh the help of default contructor ) will become null and data will be lost.

/*
I am getting error : In member function 'void linkedlist::add(std::string&)':
error: 'h' was not declared in this scope
can anyone explain me why i am getting this error message
*/
#include
#include
using namespace std;

//making class node
class node{ 
public:
friend class linkedlist;
node(){
    data = "0";
    next = NULL;
}
string data;
node* next;
};
//making class to linkedlist 
class linkedlist{

public:
linkedlist(){
    node* h = NULL;
}
//function to add data node in existing linked list
void add(string& str){
    node* newnode = new node;
    newnode->data = str;
    if(h !=NULL){
        h->next = newnode;
    }
    else{
        newnode->next = h->next;
        h->newnode;
    }
}
};

int main()
{
linkedlist l1;
string name;

//loop to enter data from user
while(true){
    cout<<"type \"q\" to exit or type name you want to add: ";
    cin>> name;
    if(name!="q"){
        l1.add(name);
    }
    else break;
}
return 0;
}