I've stumbled upon this closed question (reason - too broad): Big O operation. This question seemed really out of StackOverflow's format to me, and effectively too broad, deserving the -6 votes.
Then, I checked the recent edits, and saw this : http://stackoverflow.com/posts/22434368/revisions (edit n°3)
The OP edited his question to remove his attempted solution, and now the question seems more like a challenge than a real question with research effort, and even broader.
So, what's the correct behavior here :
- Rollback & explain that the question was better before (though, it was not that good before),
- Push the OP to improve his question through helpful comments,
- Call a moderator, it's out of my scope?