國立暨南國際大學 102 學年度第二學期 第一次期中考試卷

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).
   
   // Shorthand notation (P.73)
   // Pointers and Arrays (P.194)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int a[] = { 12, 4, 8 };
       (*a /= *(a+1) ) + *(a+2);
       cout << a[0] << 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).
   
   // Comparing Values (P.122)
   // Conditional Operator (P.133)
   #include <iostream>
   using std::endl;
   using std::cout;
   
   int main()
   {
       int i;
       for (i=0; i<10; i++)
           cout << i << (i % 5 == 0 ? '\n' : '\t');
       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).
   
   // for Loop (P.140)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       unsigned short points[] = { 82, 75, 39, 93, 2, 64, 28, 74, 9, 46 };
       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%) 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).
   
   // strlen vs. sizeof (P.190)
   #include <iostream>
   #include <cstring>
   using std::cout;
   using std::endl;
   
   int main()
   {
       char name[][10] = { "Alice", "Bob", "Charlie", "Dennis", "Emily" };
   
       cout << sizeof(name) << endl;
       cout << sizeof(name[1]) << endl;
       cout << strlen(name[1]) << endl;
       cout << sizeof(name[1][2]) << endl;
       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).
   
   // Type Conversion (P.78)
   // switch (P.135)
   #include <iostream>
   using std::cout;
   
   int main()
   {
       int even = 0, odd = 1;
       char str[] = "NETHERLANDS"; // 'A' == 65
       for (int i=0; i<12; i++)
           switch ( str[i] % 2 )
           {
               case 0:
                   even++;
                   break;
               case 1:
                   odd++;
                   break;
           }
       cout << "odd = " << odd << '\n'
            << "even = " << even << '\n';
       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).
   
   // Initialize an Array (P.172)
   #include <iostream>
   using std::cout;
   
   int main()
   {
       int data[5] = { 2 * 5 };
       int i;
       for (i=0; i<5; i+=2)
           data[i] = i;
       for (i=0; i<5; i++)
           cout << data[i];
       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).
   
   // continue (P.146) vs. break (P.136)
   #include <iostream>
   
   int main()
   {
       const int K = 5;
       int count = 0;
       int i, j;
       for (i=0; i<K; i++)
           for (j=0; j<K; j++)
           {
               ++count;
               if (i == j) break;
           }
       std::cout << count << std::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).
   
   // Increment Operator (P.74)
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       const int N = 3;
       int a[N][N] = { 0 };
       int i = 0, j = N / 2;
       for (int k=1; k <= N * N; k++)
       {
           a[i][j] = k;
           if ( ( i>0 && j<N-1 && a[i-1][j+1] > 0) || (i==0 && j==N-1) )
               ++i;
           else
           {
               if (++j >= N) j = 0;
               if (--i <  0) i = N-1;
           }
       }
   
       for (i=0; i<N; i++)
       {
           for (j=0; j<N; j++)
               cout << a[i][j];
           cout << endl;
       }
       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).

   // Substitution Cipher
   #include <iostream>
   
   int main()
   {
       char ciphertext[] = "NOGPQROHNG";
       char password[]   = "NETHERLANDS";
       char alphabet[]   = "ABCDEFGHIJKLMNOPQRSTUVWXYZ";
       char mapping[26];
       char reverse[26];
       char c;
       unsigned short i, j, k;    
       // Preparing the mapping table
       for (k=0, i=0; (c=password[i]) != '\0'; i++)    
       {
           if (alphabet[ c - 'A' ] != 0)
           {
               mapping[k++] = c;
               alphabet[ c - 'A' ] = 0;
           }
       }
       for (j=0; k<26; )
       {
           while (alphabet[j] == 0) j++;
           mapping[k++] = alphabet[j++];
       }
       // mapping[k] = '\0';
       // std::cout << "DEBUG - " << mapping << std::endl;
   
       for (i=0; i<26; i++)
           reverse[ mapping[i] - 'A' ] = 'A' + i;
   
       for (i=0; (c=ciphertext[i]) != '\0'; i++)
           std::cout << reverse[ c - 'A' ];
       std::cout << std::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).

    // 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[] = "Uiorknrsred a eCraopi oumtpler loA.tuoA.tuoA.tuo";
    
        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;
    }