UnionFind
Changing the representation of the union-find
it has the same running time but it takes just 2/3 space
! does not auto insert items /performance/
UnionFindEnum
Changing the interface - more convenient to UnionFind
Does not based on the stl data structures /it could be disadvantage/
=> does not use singular iterator assignment /not stl conform, but always work/
Just new iterator interface
MaxMatching + UnionFindTest
Using new iterator interface instead of the old