國立暨南國際大學 104 學年度第二學期 第一次期中考試卷

1. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Fundamental Data Types (P.45)
   // The sizeof Operator (P.154)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
      char a = 1;
      unsigned char b = 2;
      short c = 3;
      unsigned short d = 4;
      int e = 5;
      unsigned int f = 6;
   
      cout << sizeof(a)*sizeof(a) + sizeof(b)*sizeof(b) +
          sizeof(c)*sizeof(c) + sizeof(d)*sizeof(d) +
          sizeof(e)*sizeof(e) + sizeof(f)*sizeof(f) << endl;
      return 0;
   }
   
   
2. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Range of Values (P.45)
   // Type Conversion (P.64)
   // Overflow (P.125)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
      unsigned char b = 102;
      unsigned char a = b*b;
      unsigned short d = 65535;
      short c = static_cast<short>( d );
      int e = a + c;
   
      cout << e << endl;
      return 0;
   }
   
   
3. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // for Loop (P.140)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       unsigned short points[] = { 33, 7, 94, 68, 18, 6, 71, 70, 99, 85 };
       unsigned short K = sizeof points / sizeof( points[0] );
       unsigned short i=0, max, max2, p, p2;
       for (max=points[i++]; i < K ; i++)
       {
           if (max < points[i])
           {
               max = points[i];
               p = i;
           }
       }
   
       for (max2 = 0, i=0; i < K; i++)
       {
           if (max2 < points[i] && points[i] != max)
           {
              max2 = points[i];
              p2 = i;
           }
       }
   
       cout << p  << '\t' << max  << '\n';
       cout << p2 << '\t' << max2 << '\n';
       return 0;
   }
   
   
4. (10%) Suppose you compile and run the following code on a 64-bit computer (e.g. STU.ipv6.club.tw).  What will be its output?
   
   // Pointers to char (P.150)
   // sizeof (P.154)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       const char name[][10] = { "Alice", "Bob", "Charlie", "Dennis", "Emily" };
       const char* pstr[] = { "Alice", "Bob", "Charlie", "Dennis", "Emily" };
   
       cout << sizeof(name) << '\t'
               << sizeof(name[1]) << '\t'
               << sizeof(name[1][2]) << endl;
       cout << sizeof(pstr) << '\t'
               << pstr[1] << '\t'
               << *(pstr[1] + 2) << endl;
       return 0;
   }
   
   
5. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Type Conversion (P.64)
   // switch (P.105)
   #include <iostream>
   using std::cout;
   
   int main()
   {
       int even = 0, odd = 0;
       char str[] = "BELGIUM"; // 'A' == 65
       for (int i=0; i<7; i++)
           switch ( str[i] % 2 )
           {
               case 0:
                   even++;
               case 1:
                   odd++;
           }
       cout << "odd = " << odd << '\n'
            << "even = " << even << '\n';
       return 0;
   }
   
   
   
   
6. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // Initialize an Array (P.172)
   // Increment Operator (P.59)
   #include <iostream>
   using std::cout;
   
   int main()
   {
       int data[5] = { 3 * 5 };
       int i;
       for (i=0; i<5; ++i)
           data[i] = i;
       for (i=0; i<5; i++)
           cout << data[++i];
       return 0;
   }
   
   
7. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
   
   // continue (P.116) vs. break (P.115)
   #include <iostream>
   
   int main()
   {
       const int K = 5;
       int count = 0;
       int i, j;
       for (i=K; i>0; i--)
           for (j=K; j>0; j--)
           {
               ++count;
               if (i == j) break;
           }
       std::cout << count << std::endl;
       return 0;
   }
   

8. (10%) Determine whether the following code has syntax errors or
       not.  If it is correct, predict its output.  If it is
       incorrect, point out the
       mistake(s).
   
   // Short-Circuit
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int i, j, n = 0, m = 0;
       for (i=0; i<10; i++)
           for (j=0; j<10; j++)
               if (i<j && n++ > 0)
                   m++;
       cout << n << m << endl;
       return 0;
   }
   

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

   // Math Library
   // Type Conversion (P.63)
   #include <iostream>
   #include <cmath>
   using std::cout;
   using std::endl;
   
   int main()
   {
      cout << (9/4)+1             << '\t'
           << floor(9/4)+1        << '\t'
           << (-9/4)+1            << '\t'
           << floor(-9/4)+1       << '\t'
           << (-9.0/4)+1          << '\t'
           << floor(-9.0/4)+1     << '\n';
      return 0;
   }
   

10. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).
    // Pass by Reference
    #include <iostream>
    using std::cout;
    
    void swap1(int a, int b)
    {
      int temp;
      temp = a; a = b; b = temp;
    }
    
    void swap2(int* a, int* b)
    {
      int temp;
      temp = *a; *a = *b; *b = temp;
    }
    
    void swap3(int& a, int& b)
    {
      int temp;
      temp = a; a = b; b = temp;
    }
    
    void print(int a, int b)
    {
        cout << a << '\t' << b << '\n';
    }
    
    int main()
    {
        int x = 10;
        int y = 20;
        swap1( x,  y); print(x, y);
        swap2(*x, *y); print(x, y);
        swap3(&x, &y); print(x, y);
        return 0;
    }
    
    
11. (10%) Determine whether the following code has syntax errors or not.  If it is correct, predict its output.  If it is incorrect, point out the mistake(s).

    // Transposition Cipher
    #include <iostream>
    #include <cstring>
    using std::cout;
    using std::endl;
    
    int main()
    {
        const unsigned short N = 4;
        char matrix[N * N + 1];
        char plaintext[] = "Glp oerFo iogAlolabo iunGlt m tspscsa khrblAkaaA";
    
        char ciphertext[ sizeof(plaintext) ];
        char *p = plaintext;
        unsigned i, j;
    
        while (p < plaintext + strlen(plaintext) )
        {
        for (i=0; i<N; i++)
            for (j=0; j<N; j++)
            {
                matrix[i*N + j] = *p ? *p : 'A';
                ++p;
            }
    
        for (j=0; j<N; j++)
            for (i=0; i<N; i++)
                cout << matrix[i*N + j];
        }
        cout << endl;
    
        return 0;
    }