Recursive program for prime number (original) (raw)

Last Updated : 27 Jan, 2022

Given a number n, check whether it's prime number or not using recursion.
Examples:

Input : n = 11 Output : Yes

Input : n = 15 Output : No

The idea is based on school method to check for prime numbers.

C++ `

// CPP Program to find whether a Number
// is Prime or Not using Recursion #include <bits/stdc++.h> using namespace std;

// Returns true if n is prime, else // return false. // i is current divisor to check. bool isPrime(int n, int i = 2) { // Base cases if (n <= 2) return (n == 2) ? true : false; if (n % i == 0) return false; if (i * i > n) return true;

// Check for next divisor
return isPrime(n, i + 1);

}

// Driver Program int main() { int n = 15; if (isPrime(n)) cout << "Yes"; else cout << "No";

return 0;

}

Java

// java Program to find whether a Number // is Prime or Not using Recursion import java.util.*;

class GFG {

// Returns true if n is prime, else
// return false.
// i is current divisor to check.
static boolean isPrime(int n, int i)
{

    // Base cases
    if (n <= 2)
        return (n == 2) ? true : false;
    if (n % i == 0)
        return false;
    if (i * i > n)
        return true;
 
    // Check for next divisor
    return isPrime(n, i + 1);
}

// Driver program to test above function 
public static void main(String[] args)
{

    int n = 15;

    if (isPrime(n, 2)) 
        System.out.println("Yes");
    else 
        System.out.println("No");
}

}

// This code is contributed by Sam007.

Python3

Python 3 Program to find whether

a Number is Prime or Not using

Recursion

Returns true if n is prime, else

return false.

i is current divisor to check.

def isPrime(n, i = 2):

# Base cases
if (n <= 2):
    return True if(n == 2) else False
if (n % i == 0):
    return False
if (i * i > n):
    return True

# Check for next divisor
return isPrime(n, i + 1)

Driver Program

n = 15 if (isPrime(n)): print("Yes") else: print("No")

This code is contributed by

Smitha Dinesh Semwal

C#

// C# Program to find whether a Number // is Prime or Not using Recursion using System;

class GFG { // Returns true if n is prime, else // return false. // i is current divisor to check. static bool isPrime(int n, int i) {

    // Base cases
    if (n <= 2)
        return (n == 2) ? true : false;
    if (n % i == 0)
        return false;
    if (i * i > n)
        return true;

    // Check for next divisor
    return isPrime(n, i + 1);
}


// Driver code
static void Main()
{
int n = 15;

    if (isPrime(n, 2)) 
        Console.Write("Yes");
    else
        Console.Write("No");
} 

}

// This code is contributed by Sam007

PHP

JavaScript

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