Project Euler 269 -- Brute force for small n

#include <iostream>
#include <stdio.h>

int digit[20] = {};

bool IsRoot(long long polynomial, long long root)
{
    if (root == 0)
    {
        return polynomial % 10 == 0;
    }

    int curr_pos = 0;
    long long n = polynomial;
    do
    {
        digit[curr_pos] = n % 10;
        curr_pos++;
        n /= 10;
    }
    while (n);

    long long value = 0;
    for (int i = curr_pos-1; i >= 0; i--)
    {
        value *= root;
        value += digit[i];
    }
    return value == 0;
}

bool HasIntegerRoot(long long polynomial)
{
    for (int i = 0; i > -10; i--)
    {
        if (IsRoot(polynomial, i))
        {
            return true;
        }
    }
    return false;
}

// Z(1) 0
// Z(10) 1
// Z(100) 33
// Z(1000) 172
// Z(10000) 1754
// Z(100000) 14696
// Z(1000000) 152960
long long Z(long long k)
{
    long long count = 0;
    for (long long n = 1; n <= k; n++)
    {
        count += HasIntegerRoot(n);
    }
    return count;
}

int main(int argc, char* argv[])
{
    std::cout << Z(1) << std::endl;
    std::cout << Z(10) << std::endl;
    std::cout << Z(100) << std::endl;
    std::cout << Z(1000) << std::endl;
    std::cout << Z(10000) << std::endl;
    std::cout << Z(100000) << std::endl;
    std::cout << Z(1000000) << std::endl;
    return 0;
}