Quick-find
Quick-union
Weighted quick-union
Rather than arbitrarily connecting the second tree to the first for union(), we keep track of the size of each tree and always connect the smaller tree to the larger.
Weighted quick union with path compression
Ideally, we would like every node to link directly to the root of its tree, but
we do not want to pay the price of changing a large number of links, as we
did in the quick-find algorithm. We can approach the ideal simply by
making all the nodes that we do examine directly link to the root.
