union-find

A rust implementation of Tarjan's disjoint-set data structure with path compression optimization.

lib.rs:

Returns Some(num), num is the tag of subset in which x is. If x is not in the data structure, it returns None.
Union the subsets to which x and y belong. If it returns Ok, it is the tag for unified subset. it returns Err(), at least one of x and y is not in the disjoint-set.