Geektastic: No it wouldn't.
It would involve 3 parties that obtained no sort of majority at all...
What sort of "majority" are you looking for?
National's 46% is the largest segment of the vote, but it's not > 50%, and therefore it's also not a majority.
Geektastic: ...adding themselves together and pretending that means that someone who voted Labour also voted for the other two etc.
Nobody's pretending anything of the sort! If this happens, they'll work together on the things they can find agreement on.