Solutions to Selected Final Exam Questions

Question #6

6. The following program contains a recursive function.
a) What is the output of the program?

#include 

int recFunc(long number)
{
  if (number == 0)
    return 0;
  else
    return 1 + recFunc(number / 10);
}

void main(void)
{
  long number = 25436;
  cout << recFunc(number) << endl;
}

recFunc(25436) = 1 + recFunc(2543)
               = 1 + 1 + recFunc(254)
               = 1 + 1 + 1 + recFunc(25)
               = 1 + 1 + 1 + 1 + recFunc(2)
               = 1 + 1 + 1 + 1 + 1 + recFunc(0)
               = 1 + 1 + 1 + 1 + 1 + 0
               = 5

Given this definition of a Node:

struct Node
{
  int value;
  char letter;
  Node* link;
};

void deleteList(Node* head)
{
  if (head)
  { 
    deleteList(head->link);
    delete head;
  }
}

Using the Node struct defined in the previous problem and given this code below:

void main(void)
{
  Node* ptr1;
  Node* ptr2;
  Node* ptr3;

  ptr2 = new Node;
  ptr2->value = 5;
  ptr2->letter = 'a';
  ptr2->link = new Node;
  ptr3 = ptr2->link;
  ptr3->value = 7;
  ptr1 = new Node;
  ptr3->link = ptr1;
  ptr1->value = 7;
  ptr1->letter = 'b';
  ptr1->link = ptr2;
}

     Value         Expression
a.     5       ptr1->link->value
b.   TRUE      ptr1->value > ptr1->link->value
c. Undefined   pr1->link->link->letter
d.   TRUE      ptr1 == ptr3->link
e.    7        ptr2->link->value
f.   TRUE      ptr2->link == ptr3
g.   FALSE     pr2->letter < ptr3->link->link->letter
h.   FALSE     ptr1->link == ptr3

11. For a language to be considered an object-oriented language, it must provide 3 facilities. What are these facilities? Describe each of these facilities. (page 907)

1. Data abstraction
2. Inheritance
3. Dynamic binding (Polymorphism)

Question #12

12. Within a program, two classes can be independent of each other and have nothing in common. However, we have learned that there are 2 cases in which objects can be related. What terms do we use to define these two relationships? Explain what each term means. (page 909)

1. Inheritance
2. Composition

Question #13

13. When we derive one class from another, sometimes we want to override a function. Explain what it means to override a function. Be specific. (page 913)

Read page 913

Question #14

14. Given the Node struct defined in question #7, we've created a class called IntList that uses it to implement a linked list. Write the implementation for the Prepend public member function. You don't have to write comments, but you do have to use good programming techniques that you've learned in this class. (page 1065)

class IntList
{
  public:
    IntList(void);
    ~IntList(void);
    void Prepend(int data, char c);

  private:
    Node* head;
};

void IntList::Prepend(int data, char c)
{
  Node* newNodePtr = new Node;
  assert(newNodePtr);

  newNodePtr->value = data;
  newNodePtr->letter = c;
		
  newNodePtr->link = head;
  head = newNodePtr;
}

Below are the specifications and implementations of 3 classes: Animal, Dog, and Cat. Study them carefully. On the next page there is a short driver program that uses these classes. Answer the question below the driver code.

const int MAX_LENGTH = 50;

class Animal
{
  public:
    Animal(char *name);
    ~Animal(void);
    virtual void Speak(void);
    void Display(void);
  private:
    char name[MAX_LENGTH + 1];
};

Animal::Animal(char* n)
{
  strncpy(name, n, MAX_LENGTH);
  name[MAX_LENGTH] = NULL;
  cout << "Constructing an Animal named " << name << endl;
}

Animal::~Animal(void)
{
  cout << "Freeing an Animal named " << name << endl;
}

void Animal::Speak(void)
{
  cout << "???" << endl;
}

void Animal::Display(void)
{
  cout << name;
}
  

class Dog : public Animal
{
  public:
    Dog(char* name);
    ~Dog(void);
    void Speak(void);
};

Dog::Dog(char* name) : Animal(name)
{
  cout << "Constructing a Dog named " << name << endl;
}

Dog::~Dog(void)
{
  cout << "Freeing a Dog" << endl;
}

void Dog::Speak(void)
{
  cout << "Woof" << endl;
}

class Cat : public Animal
{
  public:
    Cat(char* name);
    ~Cat(void);
    void Speak(void);
};

Cat::Cat(char* name) : Animal(name)
{
  cout << "Constructing a Cat named " << name << endl;
}

Cat::~Cat(void)
{
  cout << "Freeing a Cat" << endl;
}

void Cat::Speak(void)
{
  cout << "Meow" << endl;
}

void main(void)
{
  Dog dog("Fido");
  Cat cat("Kitty");

  Animal* pet[2];

  pet[0] = &dog;
  pet[1] = &cat;

  pet[0]->Speak();
  pet[1]->Speak();
}

Constructing an Animal named Fido
Constructing a Dog named Fido
Constructing an Animal named Kitty
Constructing a Cat named Kitty
Woof
Meow
Freeing a Cat
Freeing an Animal named Kitty
Freeing a Dog
Freeing an Animal named Fido

struct Node
{  
  int data; 
  Node* next; 
  Node* prev;
};	

class IntList
{  
  public:    
    void Append(int data);  

  private:    
    Node* head;     
    Node* tail;
};


void IntList::Append(int data)
{
  Node* newNodePtr = new Node;
  assert(newNodePtr);

  newNodePtr->data = data;
  newNodePtr->next = NULL;
  newNodePtr->prev = NULL;

  if (!tail)		
    head = newNodePtr;
  else
  {
    tail->next = newNodePtr;
    newNodePtr->prev = tail;
  }

  tail = newNodePtr;
}