cppBinTodecFunction

#include <iostream>

int binToDec(int bin)
{
    int bit{0};
    int dec{0};

    // Sport version :)

    for (int mul{ 1 }, bit{ 0 }; (bit = bin % 10), bin and ((bit == 0 or bit == 1) ? 1 : (dec = -1, 0)); dec += bit * mul, mul *= 2, bin /= 10);

    // Simple version
    //
    //for (int mul{ 1 }; bin; mul *= 2, bin /= 10)
    //{
    //    bit = bin % 10;

    //    if (bit == 0 or bit == 1)
    //    {
    //        dec += bit * mul;
    //    }
    //    else
    //    {
    //        dec = -1;
    //        break;
    //    }
    //}
    return dec;
}

int main()
{
    int bin{ 21111111 };
    int dec{};

    std::cout << "Enter binary number\n";
    std::cin >> bin;

    dec = binToDec(bin);

    if (dec >= 0)
    {
        std::cout << "Number in dec is " << dec << '\n';
    }
    else
    {
        std::cout << "Error in bin nubber!\n";
    }

    return 0;
}