Rational to String

#include <string>
#include <vector>
#include <stdio.h>
#include <unordered_map>
#include <sstream>
#include <iostream>

using namespace std;
string rational_to_string(int numerator, int denom)
{
    std::stringstream ss;

    if(denom == 0)
    {
        ss << ((numerator < 0) ? '-' : '+') << "INF";
        return ss.str();
    }
    const bool negative = (numerator * denom < 0);
    if(negative) { ss << '-'; }

    float n(std::abs(numerator)), d(std::abs(denom));

    int integer_part;
    if(n < d)
    {
        integer_part = 0;
    }
    else
    {
        integer_part = int(n/d);
        n -= float(integer_part) * d;
    }
    ss << integer_part;

    typedef unordered_map<int, int> num_pos_map_t;
    num_pos_map_t prev_numerators;

    vector<int> frac_digits;

    size_t period_begin = INT_MAX, period_end = INT_MAX;

    for(size_t pos = 0; n > 0; ++pos)
    {
        num_pos_map_t::iterator it;
        if((it = prev_numerators.find(n)) != prev_numerators.end())
        {
            period_begin = it->second;
            period_end = pos;
            break;
        }
        prev_numerators[n] = pos;
        n *= 10.0f;

        int digit = int(n/d);
        frac_digits.push_back(digit);

        n -= digit * d;
    }


    if(!frac_digits.empty())
    {
        ss << '.';
        size_t i;
        for(i = 0; i < frac_digits.size(); ++i)
        {
            if(i == period_begin)
            {
                ss << '(';
            }
            ss << frac_digits[i];
        }

        if(i >= period_end)
        {
            ss << ')';
        }
    }

    return ss.str();
}

int main(int argc, char* argv[])
{
    std::cout << rational_to_string(0,0) << '\n';
    std::cout << rational_to_string(0,1) << '\n';
    std::cout << rational_to_string(-1,0) << '\n';
    std::cout << rational_to_string(5,3) << '\n';
    std::cout << rational_to_string(-5,3) << '\n';
    std::cout << rational_to_string(-5,-3) << '\n';
    std::cout << rational_to_string(3227,555) << '\n';
    std::cout << rational_to_string(13,720) << '\n';
    std::cout << rational_to_string(-1,57) << '\n';

    return 0;
}