hiho! is a serial contests we developed to help programmers improve their skills following some architecture. Tree, as a data struct, its most significant feature is that it can be divide in to several problem simply by its natural form, which it's similar to what we have told in "Dynamic Programming".

This time, our topic will be a little far away from what we were discussing before - "union-find algorithm". It's an easy-implement algorithm that deal with 'set' operations, and it plays very important role in the problem we will told next week!