import hash_collection
# Data structure to keeps track of elements partitioned into disjoint subsets
+#
# var s = new DisjointSet[Int]
# s.add(1)
# s.add(2)
end
# Are all elements of `es` in the same subset?
+ #
# var s = new DisjointSet[Int]
# s.add_all([1,2,3,4,5,6])
# s.union_all([1,2,3])