Imperative data structure for representing disjoint sets.
Union find is used to implement an equivalence relation on objects, where the equivalence relation can dynamically be coarsened by "union"ing two equivalence classes together.
All of the operations are effectively (amortized) constant time.
type 'a t is the type of objects, where each object is part of an
equivalence class that is associated with a single value of type
create v returns a new object in its own equivalence class that has value
union t1 t2 makes the class of
t1 and the class of
t2 be the same (if they are
already equal, then nothing changes). The value of the combined class is the value of
t2; it is unspecified which. After
union t1 t2, it will always be the
same_class t1 t2.