week-3_q2.c

/*2. Write a program in C to check a number is a
prime number or not using recursion.*/

#include<stdio.h>

int isPrime(int a, int b){
    if(a<=2)
        return a==2;
    else if(a%b==0)
        return 0;
    else if(b*b>a)
        return 1;
    return isPrime(a, b+1);
}

int main(){
    int num;
    printf("Enter the number : \n");
    scanf("%d", &num);
    isPrime(num ,2)==1 ? printf("%d is a prime number.", num) : printf("%d is not a prime number.", num); 
    return 0;
}