It has happened a few times that I have answered a question where the OP is doing things in a round-about and complicated way. I tell OP that there is a better way and show them how using a short snippet with the general approach, showing key ideas and solutions. And oft times I leave the dotting of i's and crossing of t's to the OP.

Most of the time the OP appreciates the review, and go about improving their code merrily. But every now and then there is someone that insists I provide a complete working, tested implementation for them. When this happens I feel as if I'm being used as a free-of-charge contractor. And I tell them (albeit in a more polite manner) that:

I'm not your contractor, figure it out.

The question I want to ask meta is, is it OK to do a review and not give a fully working implementation, i.e. with "some assembly required"? Or can I expect the OP to fill in the blanks if I show them the way?