Question

Convert Binary to a decimal using recursion and vice versa.

Press 1 to convert binary to decimal
Press 2 to convert decimal to binary
1
ENTER BINARY NUMBER:1111101
THE DECIMAL VALUE OF BINARY 1111101 IS 125



Press 1 to convert Binary to Decimal
Press 2 to convert Decimal to Binary
Enter your choice:2
Enter the Decimal number:125
The binary value of 125 is 1111101

Press 1 to convert Binary to Decimal
Press 2 to convert Decimal to Binary
Enter your choice:2
Enter the Decimal number:-125
The binary value of -125 is -1111101


Press 1 to convert Binary to Decimal
Press 2 to convert Decimal to Binary
Enter your choice:1
Enter the Binary number:-1111101
The decimal value of -1111101 is -125


Press 1 to convert Binary to Decimal
Press 2 to convert Decimal to Binary
Enter your choice:1
Enter the Binary number:120101
Invalid Binary number

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Code

Java

Python

Java

import java.util.*;
public class DecimalToBinaryAndViceVersaUsingRecursion
{
    public static boolean isBinaryNumbervalid(long bin)
    {
        while(bin>0)
        {
            if(bin%10>1)
            {
                System.out.println("Invalid binary number");
                return false;
            }
            bin=bin/10;
        }
        return true;
    }

    public static long BinaryToDecimalConversion(long bin,int power)
    {
        if(bin==0)
        {
            return 0;

        }

        else
        {

            return ((bin%10)*(long)Math.pow(2,power))+BinaryToDecimalConversion(bin/10,power+1);
        }
    }

    public static long DecimalBinaryConversion(long dec)
    {
        if(dec==0)
        {
            return 0;
        }
        else
        {
            return (dec%2)+10*(DecimalBinaryConversion(dec/2));
        }
    }

    public static void main()
    {
        int choice=0;
        long decimal=0,binary=0;
        Scanner sc=new Scanner(System.in);
        System.out.println("Press 1 to convert binary to decimal");
        System.out.println("Press 2 to convert decimal to binary");
        System.out.println("Enter your choice:");
        choice=sc.nextInt();
        switch(choice)
        {
            case 1:
            System.out.print("ENTER BINARY NUMBER:");
            binary=sc.nextLong();
            if(binary< 0)//negative binary number
            {
                if(isBinaryNumbervalid(-binary)==true)
                {
                    decimal=-BinaryToDecimalConversion(-binary,0);
                    /*
                    BinaryToDecimalConversion(-binary,0) will return positive decimal number
                    but we want negative decimal number so that's why
                    we added negative sign in front of BinaryToDecimalConversion(-binary,0)
                     */
                    System.out.println("THE DECIMAL VALUE OF BINARY "+binary+" IS "+decimal);
                }
            }
            else
            {
                if(isBinaryNumbervalid(binary)==true)
                {
                    decimal=BinaryToDecimalConversion(binary,0);
                    System.out.println("THE DECIMAL VALUE OF BINARY "+binary+" IS "+decimal);
                }
            }
            break;

            case 2:
            System.out.print("ENTER DECIMAL NUMBER:");
            decimal=sc.nextLong();
            if(decimal< 0)
            {
                binary=-DecimalBinaryConversion(-decimal);
                /*
                DecimalBinaryConversion(-decimal) will return positive binary number
                but we want negative binary number so that's why
                we added negative sign in front of DecimalBinaryConversion(-decimal)
                 */
                System.out.println("THE BINARY VALUE OF DECIMAL NUMBER "+decimal+" IS "+binary);
            }
            else
            {
                binary=DecimalBinaryConversion(decimal);
                System.out.println("THE BINARY VALUE OF DECIMAL NUMBER "+decimal+" IS "+binary);
            }
            break;

            default:
            System.out.println("Invalid Choice");
            break;
        }

    }
}

Python

def isBinaryNumberValid(binary):

    if(binary==0):
        return True
    if(binary%10>1):
        print("Invalid Binary number")
        return False
    else:
        return isBinaryNumberValid(binary//10)

def binaryToDecimalConvertor(binary,power=0):
    if(binary==0):
        return 0
    else:
        remainder=binary%10
        return remainder*(2**power)+binaryToDecimalConvertor(binary//10,power+1)

def decimalToBinaryConvertor(decimal):
    if(decimal==0):
        return 0
    else:
        remainder=decimal%2
        return remainder+10*decimalToBinaryConvertor(decimal//2)

if(__name__=='__main__'):
    print("Press 1 to convert Binary to Decimal")
    print("Press 2 to convert Decimal to Binary")
    choice=int(input("Enter your choice:"))
    if(choice==1):
        binaryNumber = int(input("Enter the Binary number:"))

        if (binaryNumber < 0):
            if (isBinaryNumberValid(-binaryNumber) == True):
                decimalNumber = -binaryToDecimalConvertor(-binaryNumber)
                # binaryToDecimalConvertor(-binaryNumber) will return positive decimal number
                # but we want negative decimal number so that's why
                # we added negative sign in front of binaryToDecimalConvertor(-binaryNumber)
                print("The decimal value of", binaryNumber, "is", decimalNumber)

        else:
            if (isBinaryNumberValid(binaryNumber) == True):
                decimalNumber = binaryToDecimalConvertor(binaryNumber)
                print("The decimal value of", binaryNumber, "is", decimalNumber)

    elif(choice==2):
        decimalNumber = int(input("Enter the Decimal number:"))
        if (decimalNumber < 0):
            binaryNumber = -decimalToBinaryConvertor(-decimalNumber)
            # decimalToBinaryConvertor(-decimalNumber) will return positive binary number
            # but we want negative binary number so that's why
            # we added negative sign in front of decimalToBinaryConvertor(-decimalNumber)
            print("The binary value of", decimalNumber, "is", binaryNumber)
        else:
            binaryNumber = decimalToBinaryConvertor(decimalNumber)
            print("The binary value of", decimalNumber, "is", binaryNumber)

    else:
        print("Invalid Choice Entered")