Conversion from binary to octal in c++

C++ program for Conversion from binary to octal. Here more solutions.

// Include header file
#include <iostream>
#include <string>

//  Stdc++11 program for
//  Convert Binary number into Octal number
class Convert
{
    // Convert decimal number into octal
    public:
    int octal(int number)
    {
        int result = 0;
        int multiplier = 1;
        int remainder = 0;
        while (number != 0)
        {
            remainder = number % 8;
            result = (remainder * multiplier) + result;
            multiplier *= 10;
            number = number / 8;
        }
        return result;
    }
    void binaryToOctal(std::string num)
    {
        if (num.length() == 0)
        {
            // When empty binary number
            return;
        }
        // Some useful variable
        bool flag = false;
        int decimalNo = 0;
        int counter = 0;
        int index = num.length() - 1;
        // We Assume that given binary number is valid
        // Here - indicates negative binary number
        // First convert binary to decimal
        // Example = 10111 => 23
        while (index >= 0)
        {
            if (num[index] == '1')
            {
                decimalNo += (1 << counter);
            }
            else
            {
                if (num[index] != '0')
                {
                    if (index == 0 && num[index] == '-')
                    {
                        // When get negative number
                        flag = true;
                    }
                    else
                    {
                        // Not a valid binary number
                        return;
                    }
                }
            }
            counter += 1;
            index -= 1;
        }
        // When given number is 
        int output = octal(decimalNo);
        if (flag == true)
        {
            output = -output;
        }
        // Display given number
        std::cout << "Binary : " + num;
        // Display result
        std::cout << " Octal : " << output << std::endl;
    }
};
int main(int argc, char **argv){
    Convert* task = new Convert();
    // Test Case
    task->binaryToOctal("1111");
    task->binaryToOctal("10111");
    task->binaryToOctal("101011");
    task->binaryToOctal("11011");
    task->binaryToOctal("-1000110");
    return 0;
};

Output

Binary : 1111 Octal : 17
Binary : 10111 Octal : 27
Binary : 101011 Octal : 53
Binary : 11011 Octal : 33
Binary : -1000110 Octal : -106