Question

How to find whether a number is prime or not using recursion in C++

Answer 1

#include <iostream>

int isprime_recursion(int n, int i) {
    if (i == 1) {
        return 1;
    }
    else {
       if (n % i == 0) {
         return 0;
       }
       else {
         return isprime_recursion(n, i - 1);
       }       
    }
}

int main() {
    int n = 23;
 
    if (isprime_recursion(n, n / 2)) {
        std::cout << "Prime";
    }
    else {
       std::cout << "Not prime";
    }
}



 
/*
run:
 
Prime
 
*/

 

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