Mid-Term Exam (2')
Introduction to Computer Science
NCNU CSIE

Date: December 17th, 2008
Time: 14:10-17:00
Open book; turn off computer & mobile phone

1. Check whether the following program has any syntax mistake. If yes, point out the mistakes and correct them; if no, predict the output of the program.

   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       int i, j;
       for (i=0; i<6; i++)
       {
          for (j=0; j<6; j++);
              cout << "A";
          cout << endl;
       }
       return 0;
   }
   
   

2. Check whether the following program has any syntax mistake. If yes, point out the mistakes and correct them; if no, predict the output of the
   program.
   
   #include <iostream>
   
   using namespace std;
   
   int main( void )
   {   int *ptrA, *ptrB, tmp, A=5, B=6;
   
       ptrA = &A;
       ptrB = &B;
   
       tmp = ptrA;
       ptrA = ptrB;
       ptrB = tmp;
   
       cout << "A = " << *ptrA << ", B = " <<  *ptrB << endl;
   
       return 0;
   }
   

3. What will be the output of the following program?

   #include <iostream>
   int main() // Understanding bitwise operators.
   {
         unsigned s = 2008;
   
         int i = (s >> 3) ^ ~(~0 << 2);
         std::cout << i << std::endl;
   }

4. What will be the output of the following program?

   #include <iostream>
   using namespace std;
   
   int main( void )
   {   int i=0, nums[10]={ 0 };
       while( i<10 )
       {
           if( i==5 )
           {
               ++i;
               continue;
           }
           nums[i++]=i;
       }
       for (i=0;i<10;)    
           cout << nums[i++] << " ";
           cout << endl;
       return 0;
   }

5. Please correct the following code so that the output will be
   1 1
   9 3
   6 6
   3 9
   

   // bubble_sort.c
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
      int i, j, *temp;
      int a[]  = { 1, 9, 6, 3};                    // data
      const int K = sizeof(a) / sizeof(a[0]);
      int *b[K];                                   // pdata
   
      // Initialize pdata
      for(i=0;i<K;i++)
           b[i] = &a[i];
   
      // Sort pdata by value which is pointed by pdata
      for(i=0;i<K;i++)
         for(j=K-1;j>i;j--)
          if (b[j-1] > b[j])
          {
             temp = *(b[j-1]);
             *(b[j-1]) = *(b[j]);
             *(b[j]) = temp;
          }
   
      // print values of data array & values pointed by pdata
      for(i=0;i<K;i++) 
         cout << a[i] << " " << *(b[i]) << endl;
      return 0;
   }

6. What will be the output of the following program?

   // bin2dec.c
   #include <iostream>
   using std::cout;
   using std::endl;
   
   int main()
   {
       char b[] = "1100111100";
       int n=0, i=0;
       while (b[i])
           n = (n<<1) + b[i++] - 48;
       cout << n << endl;
       return 0;
   }
   

7. Check whether the following program has any syntax mistake. If yes, point out the mistakes and correct them; if no, predict the output of the
   program.

   #include <iostream>
   
   int main()
   {
   	for (int i = 6; i < 10; i--) 
   	{
   		if (i==3)
   			break;
   		std::cout << i << std::endl;
   	}
   }
   

8. Check whether the following program has any mistake. If yes, point out the mistakes and correct them; if no, predict the output of the program.

   #include <iostream>
   using std::cout;  using std::endl;
   
   int main()
   {
       static int MAX = 5;
       int i,j,k;
       for(k=0; k<MAX; k++) ;
       for(i=1; i<=MAX; i++)
       {
           for(j=MAX; j>0; j--)
               if(i==j)
                   cout << "O";
               else
                   cout << "X";
       cout << endl;
       }
       return 0;
   }
   
   

9. Check whether the following program has any mistake. If yes, point out the mistakes and correct them; if no, predict the output of the program.
   
   #include <iostream>
   using std::endl;
   using std::cout;
   
   int main()
   {
       char a[]="Hello, world!";
       const int k = sizeof(a);
       int sum = 0;
       for(int i=0;i<k;i++)
           sum += a[i];
       cout << "k= " << k << endl;
       cout << "sum= " << sum << endl;
   
       return 0;
   }
   
   
10. Consider the following C++ program:

    #include <iostream>
    using std::cout;  using std::cin;  using std::endl;
    
    int main()
    {
        int i,j, N;
        cout << "N = ? ";
        cin >> N;
        for(i=1; i<=N; i++)
        {
            for(j=1; j<=N; j++)
                if(i==   (1)     || i==   (2)   )
                    cout << "O";
                else
                    cout << "X";
            cout << endl;
        }
        return 0;
    }
    
    			
    
    

    If we want to obtain the following results, what expressions should be filled into the three blanks, respectively?

    N = ? 5
    OXXXO
    XOXOX
    XXOXX
    XOXOX
    OXXXO
    N = ? 6
    OXXXXO
    XOXXOX
    XXOOXX
    XXOOXX
    XOXXOX
    OXXXXO