Tutorial Exercises: Set 2

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Exercise 1

Write a C program that does the following: Read a positive integer a from the user. Report whether this integer is even or odd. If a is even, assign to b the value a/2, else assign to b the value 3a+1. Print b and also whether b is even or odd.

Sample runs

Enter a positive intger: 122
122 is even
61 is odd

Enter a positive intger: 123
123 is odd
370 is even

Enter a positive intger: 124
124 is even
62 is even

Solution 1

#include <stdio.h>

int main ()
{
   unsigned int a, b;

   printf("Enter a positive intger: ");
   scanf("%u", &a);

   if (a % 2 == 0) {
      printf("%u is even\n", a);
      b = a / 2;
   } else {
      printf("%u is odd\n", a);
      b = 3 * a + 1;
   }

   printf("%u is %s\n", b, ((b & 1) == 0) ? "even" : "odd");
}

Exercise 2

Write a C program that reads a positive real number x, computes the fractional part of x, and also the rounded value of x (to the nearest integer). Your program may not make any math library calls.

Sample runs

Enter a positive real number: 1.2345
Fractional part of 1.234500 is 0.234500
Rounded value of 1.234500 is 1

Enter a positive real number: 235.5
Fractional part of 235.500000 is 0.500000
Rounded value of 235.500000 is 236

Enter a positive real number: 235.49
Fractional part of 235.490000 is 0.490000
Rounded value of 235.490000 is 235

Enter a positive real number: 235.51
Fractional part of 235.510000 is 0.510000
Rounded value of 235.510000 is 236

Solution 2

#include <stdio.h>

int main ()
{
   double x, y;
   long int a;

   printf("Enter a positive real number: ");
   scanf("%lf", &x);
   y = x - (int)x;
   printf("Fractional part of %lf is %lf\n", x, y);
   a = (int)x;
   if (y >= 0.5) ++a;
   printf("Rounded value of %lf is %ld\n", x, a);
}

Exercise 3

Write a C program that computes the two roots of the quadratic equation ax²+bx+c=0, where a,b,c are real numbers with a>0. Your program should handle complex roots also.

Sample runs

Enter the coefficients (a,b,c): 2 3 1
The roots are real: -0.500000, -1.000000

Enter the coefficients (a,b,c): 2 2 0.5
The roots are real: -0.500000, -0.500000

Enter the coefficients (a,b,c): 2 3 2
The roots are complex: (-0.750000)+i(0.661438), (-0.750000)-i(0.661438)

Solution 3

#include <stdio.h>
#include <math.h>

int main ()
{
   double a, b, c, d, x, y;

   printf("Enter the coefficients (a,b,c): ");
   scanf("%lf%lf%lf", &a, &b, &c);
   if (a == 0) {
      printf("I want a > 0\n");
   } else {
      d = b*b - 4*a*c;
      if (d >= 0) {
         x = (-b+sqrt(d))/(2*a);
         y = (-b-sqrt(d))/(2*a);
         printf("The roots are real: %lf, %lf\n", x, y);
      } else {
         d = -d;
         x = -b/(2*a);
         y = sqrt(d)/(2*a);
         printf("The roots are complex: (%lf)+i(%lf), (%lf)-i(%lf)\n", x,y,x,y);
      }
   }
}

Exercise 4

Write a C program that reads the coordinates of three points in the plane and reports which two of the three points are closest. Do not use math library calls.

Sample runs

Point 1: 1,1
Point 2: 2,2
Point 3: 4,4
Points 1,2 are closest

Point 1: 1,2
Point 2: 4,8
Point 3: 3,6
Points 2,3 are closest

Point 1: 6,2
Point 2: 1,-1
Point 3: 4,1
Points 1,3 are closest

Solution 4

#include <stdio.h>

int main ()
{
   double x1, y1, x2, y2, x3, y3;
   double d12, d13, d23;

   printf("Point 1: "); scanf("%lf,%lf", &x1, &y1);
   printf("Point 2: "); scanf("%lf,%lf", &x2, &y2);
   printf("Point 3: "); scanf("%lf,%lf", &x3, &y3);

   d12 = (x1-x2)*(x1-x2) + (y1-y2)*(y1-y2);
   d13 = (x1-x3)*(x1-x3) + (y1-y3)*(y1-y3);
   d23 = (x2-x3)*(x2-x3) + (y2-y3)*(y2-y3);

   if (d12 < d13) {
      if (d12 < d23) printf("Points 1,2 are closest\n");
      else printf("Points 2,3 are closest\n");
   } else {
      if (d13 < d23) printf("Points 1,3 are closest\n");
      else printf("Points 2,3 are closest\n");
   }
}

Exercise 5

Write a C program that reads the user's birth-place and determines whether this birth-place appears earlier or later in the dictionary than the string "kharagpur". Use the library call strcmp(). Work with strings in lower case only.

Sample runs

Enter your birth place: calcutta
"calcutta" < "kharagpur" in dictionary

Enter your birth place: kolkata
"kolkata" > "kharagpur" in dictionary

Enter your birth place: kharagpur
Your birth place is "kharagpur"

Solution 5

#include <stdio.h>
#include <string.h>

int main ()
{
   char bplace[1000], compres;

   printf("Enter your birth place: ");
   scanf("%s",bplace);
   compres = strcmp(bplace,"kharagpur");
   if (compres == 0) printf("Your birth place is \"kharagpur\"\n");
   else if (compres < 0) printf("\"%s\" < \"kharagpur\" in dictionary\n", bplace);
   else printf("\"%s\" > \"kharagpur\" in dictionary\n", bplace);
}

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