filling an array issue

So as to not start a new thread on a similar topic, where should I put the initialization within a custom library?

I find it has to be within the function it is used in within the library. i.e..

// file mylibrary.cpp
mylibrary::mylibrary(unsigned int N)
{}

void mylibrary::myfunction(unsigned int N) {
unsigned int flippedindex[N];
}

However, I would like to make flipped index an array I can access from the top-level of the library. Should I declare it as a public variable in mylibrary.h?

Sorry if I've botched up the terminology, I'm new to this.

Thanks,
memotick