How to write vector values to a file

Question

I have a large vector.

The ways that I use multiply the run-time of the program hugely. The first is write all values to a string as they are calculated using

Answer 1

Maybe I have missed something, but what is wrong with:

std::ofstream f("somefile.txt");
for(vector::const_iterator i = v.begin(); i != v.end(); ++i) {
    f << *i << '\n';
}

That avoids having to do potentially quadratic string concatenation, which I assume is what's killing your run-time.