***MORE PRACTICE QUESTIONS FOR***
CS16 Midterm Exam 2

(Practice Exam 02a—printer friendly version)
E02, 09F, Phill Conrad, UC Santa Barbara
Actual exam scheduled for: 11/18/2009

  1. (15 pts) Suppose that you are performing the selection sort algorithm—as explained in lecture, in our "field day" exercise, and in the code for lab06, i.e.


    With that in mind, indicate the values of each element of the array after the 1st, 2nd and 3rd swap.

    Keeping in mind that some of these swaps may be cases of an element being swapped with itself—those still "count" as swaps!

     
    a[0]
    a[1]
    a[2]
    a[3]
    a[4]
    initial values
    27
    6
    42
    9
    17
    after 1st swap
    after 2nd swap
    after 3rd swap
    after 4th swap (final array)
    6
    9
    17
    27
    42



  2. Suppose there is an array of integers a, and we want to swap element a[i] with element a[j], as in the following contrived example:

    int main()
{
   int a[5]={15,35,25,30,20};
   int i, j;
       int temp = 0; // iniialized to zero for no good reason.
    
   
   
       // initialize i and j
   i = 1; 
   j = 4;
   
   printf("Before: a[i] = %d  a[j]=%d \n",a[i],a[j]);
   
   // Now swap a[i] with a[j]

    

    some code goes here...

    


   // a[i] and a[j] are now swapped!

    


   printf("After:  a[i] = %d  a[j]=%d \n",a[i],a[j]);


}
    If the swap is correct, the output will be:

    Before: a[i]=35 a[j]=20
After:  a[i]=20 a[j]=35
    Below and on the next page are several attempts at writing this swap. In some cases, there is a function definition that goes along with the code.

    In each case, is the swap is correct, simply circle "CORRECT". If it is incorrect, fill in what will be printed "after" the incorrect swap is run.


    1. (4 pts) Circle CORRECT, or fill in the values: After: a[i] = _____ a[j] = ______

      function definition goes earlier in file put this at some code goes here 
      void swap(int a, int b)
      {
         int temp;
         temp = a;
         a = b;
         b = temp;
      }
               
              
      swap(a[i],a[j]);


    2. (4 pts) Circle CORRECT, or fill in the values: After: a[i] = _____ a[j] = ______

      function definition goes earlier in file put this at some code goes here 
      void swap(int *a, int *b)
      {
         int temp = 0;
         temp = (*a);
         (*a) = (*b);
         (*b) = temp;
      }
      		 
      swap(&a[i],&a[j]);

       

    3. (4 pts) Circle CORRECT, or fill in the values: After: a[i] = _____ a[j] = ______

      function definition goes earlier in file put this at some code goes here 
      (None)
               
              
      a = temp;
temp = b;
b = a;

       

    4. (4 pts) Circle CORRECT, or fill in the values: After: a[i] = _____ a[j] = ______

      function definition goes earlier in file put this at some code goes here 
      None       
              
      temp = a;
a = b;
b = temp;

       

    5. (4 pts) Circle CORRECT, or fill in the values: After: a[i] = _____ a[j] = ______

      function definition goes earlier in file put this at some code goes here 
      void swap(int *a, int i, int j)
      {
         int temp = 0;
         temp = a[i];
         a[i] = a[j];
         a[j] = temp;
      }
      
              
      swap(a,i,j);

       

End of Extra Practice Questions

Total points: ?