C Exercises: Check a number is a prime number or not

C Recursion : Exercise-12 with Solution

Write a program in C to check a number is a prime number or not using recursion.

Pictorial Presentation:

Sample Solution:

C Code:

#include

int checkForPrime(int);
int i;

int main()
{

    int n1,primeNo;

	printf("\n\n Recursion : Check a number is prime number or not :\n");
	printf("--------------------------------------------------------\n");
	
    printf(" Input any positive number : ");
    scanf("%d",&n1);
    
    i = n1/2;

    primeNo = checkForPrime(n1);//call the function checkForPrime

   if(primeNo==1)
        printf(" The number %d is a prime number. \n\n",n1);
   else
      printf(" The number %d is not a prime number. \nn",n1);
   return 0;
}

int checkForPrime(int n1)
{
    if(i==1)
    {
        return 1;
    }
    else if(n1 %i==0)
    {
         return 0;
    }     
    else
       {
         i = i -1; 
         checkForPrime(n1);//calling the function checkForPrime itself recursively
      }
}

Sample Output:

 Recursion : Check a number is prime number or not :                                                          
--------------------------------------------------------                                                      
 Input any positive number : 7                                                                                
 The number 7 is a prime number.  

Flowchart:

C Programming Code Editor:

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