Midterm Exam (2)
C++ Programming
NCNU CSIE

Date: April 8th, 2011
Time: 08:30-10:10
Open book; turn off computer & mobile phone

1. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the
   mistake(s).
   
   #include <iostream>		// Accessing Control in a Class
   #include <cstring>
   using std::cout;
   using std::endl;
   
   class CBox
   {
   	CBox(int lv, int wv, int hv):
                                   m_Length(lv), m_Width(wv), m_Height(hv){}
       int Volume() const
       { return m_Length * m_Width * m_Height; }
   
   	int m_Length;
       int m_Width;
       int m_Height;
   };
   
   int main()
   {
     CBox myBox(4, 8, 3);
   
     cout << myBox.Volume() << endl;
     return 0;
   }

2. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   

   #include <iostream>          // static data member
   #include <cstring>           
   using std::cout;
   using std::endl;
   
   class CMessage
   {
     private:
       char* pmessage;                   // Pointer to object text string
   
   
     public:
   	static int objectCount;
       // Constructor definition
   	 CMessage(const char* text = "Default message")
       {
         pmessage = new char[strlen(text) + 1];   // Allocate space for text
         strcpy(pmessage, text);                  // Copy text to new memory
   	  cout << ++objectCount << " : " << pmessage << endl;	  
       }
   
       ~CMessage()                               
   	{  delete[] pmessage; 
   		objectCount--;
   	}
   };
   
   int CMessage::objectCount = 0;
   
   void f1()
   {
   	CMessage msg1("Sunday");
   	CMessage msg2("Monday");
   }
   
   void f2()
   {
   	CMessage msg2("Tuesday");
   	CMessage msg3("Wednesday");
   }
   
   int main()
   {
     f1();	f2();
      return 0;
   }
   
   

   
   
3. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   #include <iostream>	// Assume the default pack size is 8 bytes in Visual C++
   using std::cout;
   using std::endl;
   
   class Node
   {
   	Node* left;
   	short value;
   	Node* right;
   };
   
   class C2
   {
   	Node* left;
   	double value;
   	Node* right;
   };
   
   int main()
   {
   	cout << "Node: " << sizeof(Node) << endl;
   	cout << "C2: " << sizeof(C2) << endl;
       return 0;
   }
   
   

4. (10%) What will be the output of the following program?

   #include <iostream>			
   using std::cout;
   using std::endl;
   
   int gcd(int a, int b)
   {
   	if (b == 0)	return a;
   	else		return gcd(b, a % b);
   }
   
   class CRational 
   {
     public:
       	int numerator;		// 分子
   	int denominator;	// 分母
   
   	CRational(int p=0, int q=1)	: numerator(p), denominator(q)
   	{	if (q==0)
   		{	cout << "Error! The denominator cannot be 0.\n";
   			exit(1);
   		}
   	}
   
   	void Print() 
   	{	Reduce();
   		cout << numerator;
   		if (denominator != 1)
   			cout << "/" << denominator;
   		cout << endl;
   	}
   
   	void Reduce() 
   	{	int i = gcd(numerator, denominator);
   		numerator /= i;
   		denominator /=i;
   	}
   };
      
   int main()
   {
     CRational a(12,8);
     CRational b(3,6);  
     a.Print();  b.Print();
     return 0;
   }
   
   

5. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   #include <iostream>			
   using std::cout;
   using std::endl;
   
   int gcd(int a, int b)
   {
   	if (b == 0)	return a;
   	else		return gcd(b, a % b);
   }
   
   class CRational 
   {
     public:
       	int numerator;		// 分子
   	int denominator;	// 分母
   
   	CRational(int p=0, int q=1)	: numerator(p), denominator(q)
   	{	if (q==0)
   		{	cout << "Error! The denominator cannot be 0.\n";
   			exit(1);
   		}
   	}
   
   	void Print() const	// This line is different.  Does it matter?
   	{	Reduce();
   		cout << numerator;
   		if (denominator != 1)
   			cout << "/" << denominator;
   		cout << endl;
   	}
   
   	void Reduce() 
   	{	int i = gcd(numerator, denominator);
   		numerator /= i;
   		denominator /=i;
   	}
   };
      
   int main()
   {
     CRational a(12,8);
     CRational b(3,6);  
     a.Print();  b.Print();
     return 0;
   }
   
   

6. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   #include <iostream>		// Inheritance
   #include <cstring>
   using std::cout;
   using std::endl;
   
   class CBox
   {
   public:
       CBox(int lv = 2, int wv = 3, int hv = 5):
                                   m_Length(lv), m_Width(wv), m_Height(hv){}
   private:
       int m_Length;
       int m_Width;
       int m_Height;
   };
   
   class CCandyBox: CBox
   {
     public:
       char m_Contents[10];
   
       CCandyBox(char* str = "Candy")               // Constructor
       { strcpy(m_Contents, str); }
   
       int Volume() const
   	{ return m_Length * m_Width * m_Height; }
   };
   
   int main()
   {
     CCandyBox myCandyBox;
   
     cout << myCandyBox.Volume() << endl;
     return 0;
   }
   

7. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   #include <iostream>
   #include <cstring>
   using std::cout;
   using std::endl;
   
   class CBox
   {
   public:
       CBox(int lv = 2, int wv = 3, int hv = 5):
                                   m_Length(lv), m_Width(wv), m_Height(hv){}
   protect:
       int m_Length;
       int m_Width;
       int m_Height;
   };
   
   class CCandyBox: CBox
   {
     public:
       char m_Contents[10];
   
       CCandyBox(char* str = "Candy")               // Constructor
       {     
         strcpy(m_Contents, str);
       }
       int Volume() const
       { return m_Length * m_Width * m_Height; }
   };
   
   int main()
   {
     CCandyBox myCandyBox;
   
     cout << myCandyBox.Volume() << endl;
     return 0;
   }
   
   
   
   
8. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   #include <iostream>		// Operator overloading	
   using std::cout;
   using std::endl;
   
   class CRational 
   {
     public:
       int numerator;		// 分子
   	int denominator;	// 分母
   
   	CRational(int p=0, int q=1)
   		: numerator(p), denominator(q)
   	{
   		if (q==0)
   		{
   			cout << "Error! The denominator cannot be 0.\n";
   			exit(1);
   		}
   	}
   
   	void Print()
   	{
   		cout << numerator;
   		if (denominator != 1)
   			cout << "/" << denominator;
   		cout << endl;
   	}
   
   	CRational& operator=(const CRational x) 
   	{
   		if (this == &x)
   			return *this;
   		numerator = x.numerator;
   		denominator = x.denominator;
   		return *this;
   	}
   };
      
   int main()
   {
     CRational a;
     CRational b(3);
     CRational c(1,7);
     (a = b) = c;	a.Print(); 
     a = b = c; a.Print();
     return 0;
   }
   
   
   

9. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

   #include <iostream>
   #include <cstring>
   using std::cout;
   using std::endl;
   
   class CBox
   {
   public:
       CBox(int lv = 2, int wv = 3, int hv = 5):
                                   m_Length(lv), m_Width(wv), m_Height(hv){}
       int Volume() const
       { return m_Length * m_Width * m_Height; }
   
       int m_Length;
       int m_Width;
       int m_Height;
   };
   
   class CCandyBox: protected CBox
   {
     public:
       char m_Contents[10];
   
       CCandyBox(char* str = "Candy")               // Constructor
       { strcpy(m_Contents, str); }
   };
   
   int main()
   {
     CCandyBox myCandyBox;
   
     cout << myCandyBox.Volume() << endl;
     return 0;
   }
   
   

10. (10%) Determine whether the following code has syntax erros or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
    
    #include <iostream>                    // Virtual Function
    using std::cout;
    using std::endl;
    
    class CBox                             // Base class
    {
      public:
        // Function to show the volume of an object
        void ShowVolume() const
        {
          cout << "CBox usable volume is " << Volume() << endl;
        }
    
        // Function to calculate the volume of a CBox object
        double Volume() const
        { return m_Length*m_Width*m_Height; }
    
        // Constructor
        CBox(double lv = 1.0, double wv = 1.0, double hv = 1.0)
                                :m_Length(lv), m_Width(wv), m_Height(hv) {}
    
      protected:
        double m_Length;
        double m_Width;
        double m_Height;
    };
    
    class CGlassBox: public CBox           // Derived with protected specifier
    {
      public:
        // Function to calculate volume of a CGlassBox
        // allowing 15% for packing
        double Volume() const
        { return 0.5*m_Length*m_Width*m_Height; }
    
        // Constructor
        CGlassBox(double lv, double wv, double hv): CBox(lv, wv, hv){}
    };
    
    int main()
    {
      CGlassBox myGlassBox(2.0, 3.0, 4.0);  // Declare derived box of same size
      CBox* pBox(NULL);       // Declare a pointer to base class objects
    
      pBox = &myGlassBox;        // Set pointer to derived class object
      pBox->ShowVolume();        // Display volume of derived box
      cout << pBox->Volume() << endl;
      return 0;
    }