國立暨南國際大學 102 學年度第二學期 第三次期中考試卷

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).
   
   // Pointer Arithmetic (P.194)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       const char* pstr1 = "Good morning.";
       const char* pstr2 = pstr1 + 5;
       cout << pstr2++;
       cout << pstr2 << 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).
   
   // Static variables in functions (P.283)
   #include <iostream>
   using std::endl;
   using std::cout;
   
   int pop(int n = 1)
   {
       static unsigned short array [] = { 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 };
       static unsigned short length = sizeof array / sizeof array[0];
       while (n-- > 1)
           length--;
       return array[--length];
   }
   
   int main()
   {
       cout << pop(4) << endl;
       cout << pop(2) << endl;
       cout << pop( ) << endl;
       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).
   
   // Recursive Function Calls (P.285)
   #include <iostream>
   using std::cout;
   
   void octal(int n)
   {
       if (n >= 8 )
           octal(n / 8);
       else
           cout << n % 8;
   }
   
   int main()
   {
       octal(156);
       return 0;
   }
   
   
4. (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).
   
   // Constructors (P.374)
   #include <iostream>
   using std::cout;
   
   class CRational
   {
   public:
       int numerator;
       int denominator;
   
       void Print()
       {
           cout << numerator;
           if (denominator != 1)
           {
               cout << '/' << denominator;
           }
       }
   
       Constructor(int q = 0, int p = 1)
       {
           numerator   = q;
           denominator = p;
       }
   };
   
   int main()
   {
      CRational a(1,3);
      CRational b(2);
   
      a.Print();
      b.Print();
      return 0;
   }
   
   
5. (10%) Assume that on a 64-bit computer, each pointer in C++ will occupy 8 bytes.  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).
   
   // Size of a Class
   #include <iostream>
   #include <cstring>
   using std::cout;
   using std::endl;
   
   class CText
   {
   public:
       char* ptext;
   
       CText(const char* s)
       {
           ptext = new char[strlen(s)+1];
           strcpy(ptext, s);
       }
   
       int size()
       { return sizeof(*this); }
   
       int length()
       { return strlen(ptext); }
   };
   
   int main()
   {
       CText a("NCNU"), b("MIT");
       cout << a.size() << '\t' << a.length() << endl;
       cout << b.size() << '\t' << b.length() << endl;
       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).
   
   // Destructors (P.436 - P.444)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CText
   {
   public:
       char* ptext;
   
       CText(const char* s)
       {
           ptext = new char[strlen(s)+1];
           strcpy(ptext, s);
       }
   
       ~CText()
       {
           cout << "Destructor called to release the memory ("
                   << strlen(ptext)+1 << " bytes) of "
                   << ptext << endl;
           delete [] ptext;
       }
   };
   
   int main()
   {
       CText a("Apple"), b("Banana");
       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).
   
   // Copy Constructor (P.442)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CText
   {
   public:
       char* ptext;
   
       CText(char* s = NULL)
       {
           if (s)
           {
               ptext = new char[strlen(s)+1];
               strcpy(ptext, s);
           }
           else
               ptext = static_cast<char*>(s);
       }
   
       ~CText()
       {
           if (ptext)
           {
               cout << "Destructor called for "
                       << ptext << endl;
           }
           else
           {
               cout << "Destructor called, but no memory needs to be releases."
                           << endl;
           }
       }
   };
   
   int main()
   {
       CText c("Coconut");
       CText a(c);
       a.ptext += 4;
       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).
   
   // Overloading the Addition Operator (P.459)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   class CData
   {
   public:
       int* pdata;
   
       CData(int v = 0)
       { pdata = new int(v); }
   
       CData Add(CData d)
       { return CData(*pdata = *d.pdata); }
   
       CData operator+(CData d)
       { return Add(d); }
   
       void Print()
       { cout << *pdata << endl; }
   };
   
   int main()
   {
       CData a(5), b(3);
       CData c;
       c = a + b;
       a.Print();
       c.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).

   // Searching Strings (P.523)
   #include <iostream>
   #include <string>
   using std::cout;
   using std::endl;
   using std::string;
   int o(string a, string b)
   {
       int c = 0, p = 0;
       while ( a.find(b, p) <= a.length() )
       {
           p = a.find(b, p) + 1 ;
           c++;
       }
       return c;
   }
   
   int main()
   {
       string a("NCCU");
       string b("C");
       cout << o(a, b) << endl;
       cout << o(a, b+"U") << endl;
       cout << o(a, "NCNU") << 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).

    // The Size of a Vector (P.655)
    #include <iostream>
    #include <string>
    #include <vector>
    using std::cout;
    using std::endl;
    using std::string;
    using std::vector;    
    
    int main()
    {
        vector<int> a(10);
        int b = 5;
        int c = 27;
    
        cout << a.size() << endl;
        a.push_back(b);
        a.push_back(c);
        cout << a.size() << endl;
    
        return 0;
    }