cheese.cpp

#include <sstream>
#include <iostream>
#include <iomanip>
#include <cmath>

unsigned long quickdigitalroot(unsigned long num) {
    return num - std::floor( ( (double)num - 1.0) / 9.0 );
}

bool is10InDigitalRoot(unsigned long num) {
    long dr = 0;
    while (num > 0) {
        dr += num % 10;
        num /= 10;
    }

    if (dr > 10) { // keep going
        is10InDigitalRoot(dr);
    }

    if (dr == 10) { // yes, yes it is
        return true;
    }

    return false;
}

unsigned long decAsHexToDec(unsigned long num)
{
    unsigned long result = 0;
    long pow_idx = 0;
    while (num > 0) {
        long dig = num % 10;
        result += dig * pow(16, pow_idx);
        pow_idx++;
        num /= 10;
    }

    return result;
}

long attempts = 0;

void cheese(unsigned long start_number, long start_bit = 0, long bits_left = 9)
{
    if (bits_left == 0)
    {
        attempts++;

        unsigned long readashex = decAsHexToDec(start_number);
        // long dr = quickdigitalroot(readashex);
        bool dr = is10InDigitalRoot(readashex);
        if (dr && readashex != 1)
            std::cout << std::left << std::setw(12) << start_number << " fits " << " ashex " << readashex << std::endl;
        else
            std::cerr << "\r" << start_number << " attempt: " << attempts << " as hex: " << readashex << " dr: " << dr << "       "; 
        return;
    }

    unsigned long bit_n = 1 << start_bit;
    if ( (start_number & bit_n) == 0 ) {
        // number is not preset

        if (start_bit + bits_left < 32) {
            // with ith bit on
            cheese(start_number | bit_n, start_bit + 1, bits_left - 1);
            // without ith bit on
            cheese(start_number, start_bit + 1, bits_left);
        }
    }
}

int main() {
    cheese(1 << 30);

    return 0;
}