c++拓扑排序。对一个有向无环图G进行拓扑排序 -C++ topological sort, using vc2008 MFC framework implementations. In a Directed Acyclic Graph (Directed Acyclic Graph DAG) G for topological sort

Helper function: return distance(first, last) for forward iterators, or 0 for input iterators. -Helper function: return distance(first, last) for forward iterators, or 0 for input iterators.