C Interview Questions

Question-131. Write a program to swap two numbers without using third variable ?

Answer-

#include    
#include    
main()    
{    
int a=10, b=20;      
clrscr();      
printf("Before swap a=%d b=%d",a,b);      

a=a+b;//a=30 (10+20)    
b=a-b;//b=10 (30-20)    
a=a-b;//a=20 (30-10)    

printf("\nAfter swap a=%d b=%d",a,b);    
getch();    
}

Question-132. Write a program to print fibonacci series without using recursion ?

Answer-

#include    
#include    
void main()    
{    
 int n1=0,n2=1,n3,i,number;    
 clrscr();    
 printf("Enter the number of elements:");    
 scanf("%d",&number);    
 printf("\n%d %d",n1,n2);//printing 0 and 1    

 for(i=2;i<number;++i)//loop starts from 2 because 0 and 1 are already printed    
 {    
  n3=n1+n2;    
  printf(" %d",n3);    
  n1=n2;    
  n2=n3;    
 }    
getch();    
}

Question-133. Write a program to print fibonacci series using recursion ?

Answer-

  #include    
#include    
void printFibonacci(int n){    
    static int n1=0,n2=1,n3;    
    if(n>0){    
         n3 = n1 + n2;    
         n1 = n2;    
         n2 = n3;    
         printf("%d ",n3);    
         printFibonacci(n-1);    
    }    
}    
void main(){    
    int n;    
    clrscr();    
    printf("Enter the number of elements: ");    
    scanf("%d",&n);    

    printf("Fibonacci Series: ");    
    printf("%d %d ",0,1);    
    printFibonacci(n-2);//n-2 because 2 numbers are already printed    

    getch();    
}

Question-134. Write a program to check prime number in C Programming ?

Answer-

  #include    
#include    
void main()    
{    
int n,i,m=0,flag=0;    
clrscr();    
printf("Enter the number to check prime:");    
scanf("%d",&n);    
m=n/2;    
for(i=2;i<=m;i++)    
{    
if(n%i==0)    
{    
printf("Number is not prime");    
flag=1;    
break;    
}    
}    
if(flag==0)    
printf("Number is prime");    
getch();    
}

Question-135. a program to check palindrome number in C Programming ?

Answer-

  #include    
#include    
main()    
{    
int n,r,sum=0,temp;    
clrscr();    
printf("enter the number=");    
scanf("%d",&n);    
temp=n;    
while(n>0)    
{    
r=n%10;    
sum=(sum*10)+r;    
n=n/10;    
}    
if(temp==sum)    
printf("palindrome number ");    
else    
printf("not palindrome");    
getch();    
}

Question-136. Write a program to print factorial of given number without using recursion ?

Answer-

  #include    
#include    
void main(){    
  int i,fact=1,number;    
  clrscr();    
  printf("Enter a number: ");    
  scanf("%d",&number);    

  for(i=1;i<=number;i++){    
      fact=fact*i;    
  }    
  printf("Factorial of %d is: %d",number,fact);    
  getch();    
}

Question-137. Write a program to print factorial of given number using recursion ?

Answer-

  #include    
#include    

long factorial(int n)    
{    
  if (n == 0)    
    return 1;    
  else    
    return(n * factorial(n-1));    
}    

void main()    
{    
  int number;    
  long fact;    
  clrscr();    
  printf("Enter a number: ");    
  scanf("%d", &number);     

  fact = factorial(number);    
  printf("Factorial of %d is %ld\n", number, fact);    
  getch();    
}

Question-138. Write a program to check armstrong number in C ?

Answer-

#include    
#include    
main()    
{    
int n,r,sum=0,temp;    
clrscr();    
printf("enter the number=");    
scanf("%d",&n);    
temp=n;    
while(n>0)    
{    
r=n%10;    
sum=sum+(r*r*r);    
n=n/10;    
}    
if(temp==sum)    
printf("armstrong  number ");    
else    
printf("not armstrong number");    
getch();    
}

Question-139. Write a program to reverse a given number in C ?

Answer-

  #include    
#include    
main()    
{    
int n, reverse=0, rem;    
clrscr();    
printf("Enter a number: ");    
  scanf("%d", &n);    
  while(n!=0)    
  {    
     rem=n%10;    
     reverse=reverse*10+rem;    
     n/=10;    
  }    
  printf("Reversed Number: %d",reverse);    
getch();    
}