Question

Program to convert binary to decimal number using recursion

				
					Enter the Binary number:111001
The decimal value of 111001 is 57

Enter the Binary number:-111001
The decimal value of 111001 is -57


Enter the Binary number:110002
Invalid Binary number

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Code

Java

Python

Java

				
					import java.util.Scanner;
public class BinaryToDecimal
{
    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 void main()
    {
        long decimal=0,binary=0;
        Scanner sc=new Scanner(System.in);

        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 thats 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);
            }
        }

       
    }
}

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)

if(__name__=='__main__'):
    decimalNumber=0
    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 thats 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)