Generating binary sequences

Given n bits, I need to generate all possible n bit binary sequences in order of most zeros to least zeros. For the n Choose k sequences with k zeros, the order doesn't really matter.
Ie if n=3 I need to generate the sequence:

000, 001, 010, 100, 011, 101, 110, 111

How the hell do I do this as efficiently as possible (or at all)? Intuition tells me to form a binary tree of 0's and 1's and somehow parse it, but I can't seem to figure out how to do that.
Any suggestions? I'm using C++, though this seems to be more of an algorithmic question than depending on any specific language feature.

Thanks.