Efficient way to convert int to string

Question

I'm creating a game in which I have a main loop. During one cycle of this loop, I have to convert int value to string about ~50-100 times. So far I've been using this function:

std::string Util::intToString(int val)
{
   std::ostringstream s;
   s << val;
   return s.str();
}

But it doesn't seem to be quite efficient as I've encountered FPS drop from ~120 (without using this function) to ~95 (while using it).

Is there any other way to convert int to string that would be much more efficient than my function?

Answer 1

It's 1-72 range. I don't have to deal with negatives.

Pre-create an array/vector of 73 string objects, and use an index to get your string. Returning a const reference will let you save on allocations/deallocations, too:

// Initialize smallNumbers to strings "0", "1", "2", ...
static vector<string> smallNumbers;

const string& smallIntToString(unsigned int val) {
    return smallNumbers[val < smallNumbers.size() ? val : 0];
}