Question 5:

a) compilation error, I has a pure virtual method,
   cannot be instantiated
b) okay.
c) okay.
d) okay.
e) okay.
f) okay.
g) compilation error, type E of e is not a subclass of
   type I of variable l
h) okay.
i) compilation error, type C of c is not a subclass of
   type D of variable g (but the other way round)
j) okay. h becomes NULL.
k) okay. h becomes d (a D* pointer)
l) okay.
m) okay.
n) okay.
o) compilation error, same reason as in g).

---------------------------------------------------

Question 4:

template<typename T, bool isend(T)>
int read(List<T> &list)
{
  int n = 0;
  while (true)
  {
    T x;
    cin >> x;
    if (!cin) return -1;
    if (isend(x)) return n;
    list.push_back(x);
    n++;
  }
}

template <typename T> class List
{
  Node<T>* head;
  Node<T>* tail;
  int len;

  List(): head(NULL), tail(NULL), len(0) { ... }
  void push_back(T& x)
  {
    Node<T> *node = new Node<T>(x, NULL);
    if (tail == NULL)
      head = node;
    else
      tail->next = node;
    tail = node;
    len++;
  }

}

-----
Question 3:

template<class T>
class ArrayQueue: public BoundedQueue<T>
{
  T* a; int l; int n; int h; int t;
public:
  ArrayQueue(int s): a(new T[s]), l(s), n(0), h(0), t(0) { }
  ~ArrayQueue() { delete[] a; }
  bool isempty() { return n == 0; }
  bool isfull() { return n == l; }
  void put(T& x)
  {
    a[t] = x;
    // t = t+1; if (t == l) t = 0;
    t = (t+1)%l;
    n++;
  }
  T get()
  {
    T x = a[h];
    h = (h+1)%l;
    n--:
    return x;
  }
}

-------------------------------------------------------------

Question 2:

set<string> getSales(Shop& shop, set<int>& days, int& turnover)
{
  set<string> names;
  turnover = 0;
  list<Sale*> sales = shop.sales();
  for (list<Sale*>::iterator it = sales.begin();
       it != sales.end; it++)
  {
    Sale* sale = *it;
    int day = sale->getDay();
    if (days.count(day) == 0) continue;
    addSales(shop, *sale, names, turnover);
  }
  return names;
}

void addSales(Shop& shop, Sale& sale, set<string>& names,
              int& turnover)
{
  map<string,Article*> articles = shop.articles();
  list<string> ids = sale.articleIds();
  for (list<string>::iterator it = ids.begin();
       it != ids.end(); it++)
  {
    string id = *it;
    Article* article = articles.find(id);
    string name = article->getName();
    int price = article->getPrice();
    names.insert(name);
    turnover += price;
  }
}

---------------
Question 1:

class Work {
  int m; // minutes
  int r; // cent/minute
public:
  Work(int m0, int r0): m(m0), r(r0) { }
  Work(Work& w): m(w.m), r(w.r) { } // automatically generated
  void printSalary()
  {
    int s = m*r;
    cout << (s/100) << "," << (s%100) << endl;
  }
  void add(int m) { this->m += m; }
  bool subtract(int m)
  {
    if (this->m < m) return false;
    this->m -= m;
    return true;
  }
  static void reset(Work& w) { w.m = 0; }
  void reset() { m = 0; }
  int compare(Work& w)
  {
    int s1 = m*r;
    int s2 = w.m*w.r;
    if (s1 == s2) return 0;
    if (s1 > s2) return 1;
    return -1;
  }
};