Code Nhập giới hạn phần tử

#include <iostream>
#include <fstream>
using namespace std;
//dinh nghia 1 node. trong c++ chung ta khong can tu struct nua
struct Node
{
    int x;
    Node *pNext;
};

//1 list Lifo hay Fifo thi ta deu co the quan ly bang 2 con tro co ban nay. Nhu vay thao tac se de hon so voi 1 con tro first
struct List
{
    Node *pHead;
    Node *pTail;
};

//Khoi tao 1 List trong, khong co phan tu nao
void CreateList(List &L)
{
    L.pHead = L.pTail = NULL;
}

//Khoi tao 1 node co gia tri x
Node *CreateNode(int x)
{
    Node *p = new Node;
    //Kiem tra neu khong du bo nho de cap phat thi thoat luon
    if (p == NULL)
        exit(1);
    p->pNext = NULL;
    p->x = x;
    return p;
}

//Them 1 Node vao dau danh sach. cai nay danh cho LIFO
void AddHead(List &L, Node *pAdd)
{
    if (L.pHead == NULL)
    {
        L.pHead = L.pTail = pAdd;
    }
    else
    {
        pAdd->pNext = L.pHead;
        L.pHead = pAdd;
    }
}

//Them 1 Node vao cuoi danh sach. cai nay danh cho FIFO
void AddTail(List &L, Node *pAdd)
{
    if (L.pHead == NULL)
    {
        L.pHead = L.pTail = pAdd;
    }
    else
    {
        L.pTail->pNext = pAdd;
        L.pTail = pAdd;
    }
}

//Duyet cac phan tu trong List ra de xem
void Output(List L)
{
    Node *p = L.pHead;
    while (p != NULL)
    {
        cout << " " << p->x;
        p = p->pNext;
    }
}

//Doc tep vao danh sach LIFO
void ReadFile(List &L)
{
    //thay vi dung ifstream de doc minh dung lop tong quat hon la fstream va dung mode la ca in va out
    fstream f;
    int x;
    f.open("D:\\input.txt", ios::in | ios::out);
    if (!f)
        cout << "tep khong ton tai\n";
    else
    {
        while (!f.eof())
        {
            f >> x;
            //Tao node co gia tri x va them vao dau danh sach fifo
            AddHead(L, CreateNode(x));
        }
    }
    f.close();
}

//Lay phan tu chan duong trong lifo chuyen sang fifo
void Lifo_Fifo(List Fifo, List &Lifo)
{
    Node *p = Fifo.pHead;
    while (p != NULL)
    {
        if (p->x > 0 && p->x % 2 == 0)
        {
            //Tao node co gia tri p->x va them vao danh sach lifo
            AddTail(Lifo, CreateNode(p->x));
        }
        p = p->pNext;
    }
}

void Input(List &L, int Max)
{
    int x;
    cout << "Viec nhap se ket thuc khi nhap gia tri x = 0\nNhap danh sach LIFO\n";
    while (Max > 0)
    {
        cout << "x = ";
        cin >> x;
        if (x == 0) break;
        AddHead(L, CreateNode(x));
        Max--;
    }
}


void main()
{
    List Fifo, Lifo;
    //Khoi tao 2 list
    CreateList(Fifo);
    CreateList(Lifo);

    //Nhap du lieu vao Lifo va xuat ra man hinh
    //Tam thoi khuc nay minh gioi han 5 phan tu. ban co the cin >> n va truyen n vao de nhap n phan tu
    Input(Lifo, 5);
    Output(Lifo);

    cout << endl;

    //Doc du lieu vao Fifo va xuat ra man hinh
    Lifo_Fifo(Lifo, Fifo);
    Output(Fifo);
}