1a. (10 points) You have a two-dimensional array of characters that has NROWS (number of rows) and NCOLS (number of columns). NROWS and NCOLS are odd global constants.

a. Write function fill() that sets the middle row and middle column to the character X and the rest of the array elements to the character O.


b. Write function pretty_print() that displays the array with NCOLS values per line and one space separating the characters. A 5x7 array would be displayed like this:

      O O O X O O O
      0 O O X O O O
      X X X X X X X
      O O O X O O O
      O O O X O O O

1b. (10 points) You have an integer array of size N where N is a global constant. Write function max_min() that finds (and returns through the parameter list) 1) the largest value in the array, 2) the smallest value in the array, 3) the number of times the smallest appears, and 4) the number of times the largest appears. Use a single loop.

2. (8 points) You have the following class definition.

    class Test2  {

      public:
        Test2();                    // default constructor
        Test2(int, int, char*);     // parametrized constructor

      private:
        int x,         // range 0 through 99
            y;         // range 0 through 10
        char a[21];    // C-style string, requires srtcpy() to copy
    } 

a. Write the code for the default constructor where the integer data members are set to 0, and the string is set to the null string ''.


b. Write the code for the parametrized constructor. Check for valid integers and appropriate string length. If out of range, set to the defaults.


c. Create an object obj1 with default values.



d. Create an object obj2 with arguments 5, 8, "test two".

        struct course  {
          char title[21];
          char day[3], grade;
          int hours;
        };

        struct course schedule[10], extra;     // assume initialization

a.  Write one line of code to copy   extra   into the first structure in schedule.




b.  Assign a four to the hours field of the last structure in schedule.


c.  Write one statement to copy the string "ECE 206" to the title field of the first structure in schedule.


7. (6 points) You have an array-based linked list with an alphabetic list pointed to by first.

              data     link           first:  (see part c)
          -----------|------
        0 |   Lee    | -1  |          next:   5
          -----------|------
        1 |   Jim    |  0  |
          -----------|------          
        2 |   Ike    |  1  |
          -----------|------
        3 |   Amy    |  4  |
          -----------|------
        4 |   Bev    |  2  |
          -----------|------
        5 |          |     |
          -----------|------

a.  In what order were the names seen in the input data?


b.  Very neatly, show what happens in the arrays when we add Dan.

c.  What signifies an empty list?







8. (6 points) Answer the following questions.

a. What is the primary disadvantage of binary search?


b. What are the two things that new does?

c. What are the two things that delete does?

9. (3 points) You have int a[7] = {24, 37, 12, 64, 19, 45, 71}; Show the array elements after the first pass of selection sort as shown in class. ------------------------------------------- pass 1: | | | | | | | | | | | | | | | | ------------------------------------------- 0 1 2 3 4 5 6


10. (8 points) Write function count_ch() that returns the number of times character ch is in C-style string word. Determine the length of the string with either strlen() or use the string terminating "NULL" character, written as '\0', to end your for loop. We have supplied the header for you.

       int count_ch(char word[], char ch)

11. (6 points) Answer the following questions about C-style strings. Recall that C-style strings are character arrays that are terminated by the "NULL" character, which is written '\0'.

      char s1[32] = "Almost the end of the semester!";
      char s2[5] = "EECS";
      char *s3 = "EECS";

a. Is a positive number, a negative number, or zero printed by
        cout << strcmp(s1, s3) << endl; ?


b. Is a positive number, a negative number, or zero printed by
        cout << strcmp(s2, s3) << endl; ?


c. What does strchr(s3, 'E') do? Be brief but clear.




12. (4 points) Declare a file fin and open it for input from file in.dat.





13. (6 points) What gets printed from the C++ program below?

    #include<iostream>
    using namespace std;

    void ptr_func(int, int *);

    int main()
    {
      int i, y;
      int *p;

      p = &i;   
      i = y = 33;         

      cout << "Before call to ptr_func(): " << i << "  " << *p << endl;
      ptr_func(i, p);
      cout << "After call to ptr_func():  " 
           << i << "  " << *p << "  " << y << endl;

      *p = 55;
      cout << "Result:  " << i << "  " << *p << endl;

      return 0;
    }

    void ptr_func(int x, int *ptr)
    {
      int y;      // y is local to ptr_func()

      cout << "During call to ptr_func(): " << x << "  " << *ptr << endl;
      x = 22;
      y = 44;
      *ptr = 77;
    }




Key for CS 102/ECE 206 Test 2, April 27, 2010

1a. 
void fill (char a[][NCOLS])
{
  int row, col;
  for (row = 0; row < NROWS; row++)
    for (col = 0; col < NCOLS; col++)
      a[row][col] = 'O';

  for (row = 0; row < NROWS; row++)
    a[row][NCOLS / 2] = 'X';

  for (col = 0; col < NCOLS; col++)
      a[NROWS / 2][col] = 'X';
}

void pretty_print (char a[][NCOLS])
{
  int row, col;
  for (row = 0; row < NROWS; row++)
    for (col = 0; col < NCOLS; col++)  {
      cout << a[row][col] << " ";
      if (col == NCOLS - 1)  cout << endl;
    }

}

1b. 
void max_min(int a[], int *max, int *min, int *cmax, int *cmin)
{
  int i;

  *max = *min = a[0];
  *cmax = *cmin = 1;

  for (i = 1; i < N; i++)  {
    if (a[i] == *max)  *cmax += 1;
    if (a[i] == *min)  *cmin += 1;

    if (a[i] > *max)  {
      *max = a[i];
      *cmax = 1;
    }

    if (a[i] < *min)  {
      *min = a[i];
      *cmin = 1;
    }
  }

}


2a.
    Test2::Test2()                    // default constructor
    {
      x = y = 0;
      strcpy (a, "");
    }

b. Mystery::Mystery(int m, int n, char *s)     // parameterized constructor
   {
     cout << m << "  " << n << "  " << endl << endl;
       m >= 0 && m <= 25 ? x = m : x = 0;
       n >= 0 && n <= 10 ? x = n : y = 0;
       strlen(s) <= 20 ? strcpy(a, s) : strcpy(a, "");
    }

    Or, use if-else.

c. Test2 obj1;

d. Test2 obj2 (5, 8, "test two");



3. Size of vector:  3
   In func():  
   10  11  20  
   42  21  31  
   In main():  
   10  11  20  
   20  21  22  

4. a. Indicates the actual number of elements in the vector.
   b. Checks the index boundaries.

5.  (a)  valid    -  address of a[0]
    (b)  invalid  -  a is a constant pointer.
    (c)  valid    -  3
    (d)  valid    -  0
    (e)  valid    -  4
    (f)  valid    -  address of a[3]
    (g)  invalid  -  &a is a double pointer and p is not

6. a. schedule[0] = extra;
   b. schedule[9].hours = 4;
   c. strcpy(schedule[0].title, "ECE 206");



7. a. Lee  Jim  Ike  Amy  Bev

   b.     -----------|------
        0 |   Lee    | -1  |          
          -----------|------
        1 |   Jim    |  0  |
          -----------|------
        2 |   Ike    |  1  |
          -----------|------
        3 |   Amy    |  4  |
          -----------|------
        4 |   Bev    |  5  |     Note: only link[4] and [5] are changed
          -----------|------
        5 |   Dan    |  2  |     Dan is added here.
          -----------|------

   c. first holds -1

8a. The list must be sorted.

 b. 1. allocates space from the heap (or freestore) for the variable, and
    2. assigns the address of the space to the pointer
 
 c. 1. returns the space to the heap (or freestore), and
    2. the pointer is now undefined.

9. 12  37  24  64  19  45  71

10. Lots of correct ways to write this - if you are stuck, come see me.

11. a. negative     b. zero
    c. returns a pointer to (or the address of) the first instance
       of the character 'E' in the string.

12. ifstream fin;
    fin.open(in.dat");

13.  Before call to ptr_func(): 33  33
     During call to ptr_func(): 33  33
     After call to ptr_func():  77  77  33
     Result:  55  55