Tutorial Exercises: Set 5

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Exercise 1

Write a structure to represent an element of the form a+sqrt(-2)b for integer values a and b. Write a C function that takes two such complex numbers and returns the product of these numbers in the same form.

Solution 1

   typedef struct {
      int a;
      int b;
   } comp2;

   comp2 mul ( comp2 z1 , comp2 z2 )
   {
      comp2 z;

      z.a = (z1.a)*(z2.a) - 2*(z1.b)*(z2.b);
      z.b = (z1.a)*(z2.b) + (z1.b)*(z2.a);
      return z;
   }

Exercise 2

Consider the following type definitions.

   typedef struct {
      char name[80];
      char rollno[8];
      float cgpa;
   } stud1;

   typedef struct {
      char *name;
      char *rollno;
      float cgpa;
   } stud2;

   typedef stud1 *stud1ptr;
   typedef stud2 *stud2ptr;

   typedef stud1 stud1arr[100];
   typedef stud2 stud2arr[100];

Assume that a pointer is of size 32 bits. Determine the following sizes:

   sizeof(stud1)
   sizeof(stud2)
   sizeof(stud1ptr)
   sizeof(stud2ptr)
   sizeof(stud1arr)
   sizeof(stud2arr)

Solution 2

   sizeof(stud1) = 80 + 8 + 4 = 92
   sizeof(stud2) = 4 + 4 + 4 = 12

   sizeof(stud1ptr) = 4
   sizeof(stud2ptr) = 4

   sizeof(stud1arr) = 92 x 100 = 9200
   sizeof(stud2arr) = 12 x 100 = 1200

Exercise 3

Write a C function that accepts a non-empty array of complex numbers and returns the array element having the maximum magnitude.

Solution 3

   typedef struct {
      double re;
      double im;
   } complex;

   complex maxmag ( complex A[] , int n )
   {
      int i, maxidx;
      double t, max;

      max = A[0].re * A[0].re + A[0].im * A[0].im;
      maxidx = 0;
      for (i = 1; i < n; ++i) {
         t = A[i].re * A[i].re + A[i].im * A[i].im;
         if (t > max) {
            max = t;
            maxidx = i;
         }
      }
      return A[maxidx];
   }

Exercise 4

Consider a student record of the form:

   typedef struct {
      char *name;
      char *rollno;
      float cgpa;
   } strud;

Write a C function that accepts two strings and a floating point number, allocates the exact amount of memory in a stud data type in order to store the name and the roll number, populates the structure with the arguments and returns the structure. Also show a sample way of calling this function with some constant arguments.

Solution 4

   stud init ( char *nptr, char *rptr, float c )
   {
      stud s;

      s.name = (char *)malloc((strlen(nptr)+1)*sizsof(char));
      s.rollno = (char *)malloc((strlen(rptr)+1)*sizsof(char));
      strcpy(s.name,nptr);
      strcpy(s.rollno,rptr);
      s.cgpa = c;
      return s;
   }

   ...

   init("Foolan Barik", "07FB1331", 9.89);

Exercise 5

Consider a linked list with each node containing the following fields:

   typedef struct _node {
      int key;
      int flag;
      struct _node *next;
   } node;

   typedef node *nodep;

Write a function that accepts a header of type nodep to a linked list and that finds the sum of the key values stored in only those nodes in the linked list for which the flag values are non-zero.

Solution 5

   int sum ( nodep p )
   {
      int sum = 0;

      while (p != NULL) {
         if (p -> flag) sum += p -> key;
         p = p -> next;
      }
      return sum;
   }

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