Question

Check whether two numbers are twin prime using recursion.

**A twin prime is a prime number that is either 2 less or 2 more than another prime number—for example, either member of the twin prime pair (41, 43)**

				
					ENTER FIRST NUMBER
41
ENTER SECOND NUMBER
43
41 AND 43 ARE TWIN PRIME NUMBERS

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Code

Java

Python

Java

				
					import java.util.Scanner;
public class TwinPrimeUsingRecursion
{
    public static boolean isPrime(int n,int i)
    {
        if(n<=1)
        {
            return false;
        }

        else if(i==n)
        {
            return true;
        }

        else if(n%i==0)
        {
            return false;
        }
        else
        {
            return  isPrime(n,(i+1));
        }
    }

    public static void main()
    {
        int firstNumber=0,secondNumber=0,difference=0;
        boolean isFirstNumberPrime=false,isSecondNumberPrime=false;
        Scanner sc=new Scanner(System.in);
        System.out.println("ENTER FIRST NUMBER:");
        firstNumber=sc.nextInt();
        System.out.println("ENTER SECOND NUMBER:");
        secondNumber=sc.nextInt();
        isFirstNumberPrime=isPrime(firstNumber,2);
        isSecondNumberPrime=isPrime(secondNumber,2);

        difference=Math.abs(firstNumber-secondNumber);
        // checking if the difference between two numbers is equal to 2
        // else both the number is not twin prime numbers
        if(difference==2)
        {
            if(isFirstNumberPrime==false || isSecondNumberPrime==false)
            {
               System.out.println(firstNumber+" AND "+secondNumber+" ARE NOT TWIN PRIME NUMBERS");

            }
            else
            {
                System.out.println(firstNumber+" AND "+secondNumber+" ARE TWIN PRIME NUMBERS");
            }
        }
        else
        {
            System.out.println(firstNumber+" AND "+secondNumber+" ARE NOT TWIN PRIME NUMBERS");
        }
    }
}

Python

				
					def isPrime(n,i=2):
    if(n<=1):
        return False
    elif(i==n):
        return True
    elif(n%i==0):
        return False
    else:
        return isPrime(n,i+1)

if(__name__=='__main__'):
    lowerRange=int(input("Enter the lower value:"))
    upperRange = int(input("Enter the upper value:"))
    print("Twin Prime numbers between",lowerRange,"and",upperRange,":")
    for i in range(lowerRange,upperRange-1):
        firstNumber=i
        secondNumber=i+2
        isFirstNumberPrime=isPrime(firstNumber)
        isSecondNumberPrime=isPrime(secondNumber)
        if(isFirstNumberPrime==True and isSecondNumberPrime==True):
            print("(",firstNumber,",",secondNumber,")")