///Using this it is possible to avoid the superfluous memory

     /// Using this it is possible to avoid the superfluous memory

     ///allocation: if you know that the graph you want to build will

     /// allocation: if you know that the graph you want to build will

     ///contain at least 10 million nodes then it is worth reserving

     /// be very large (e.g. it will contain millions of nodes and/or edges)

     ///space for this amount before starting to build the graph.

     /// then it is worth reserving space for this amount before starting

     void reserveNode(int n) { nodes.reserve(n); };

     /// to build the graph.

     /// \sa reserveNode

     /// \brief Using this it is possible to avoid the superfluous memory

     void reserveEdge(int m) { edges.reserve(m); };

     /// allocation.

     ///Using this it is possible to avoid the superfluous memory

     ///allocation: see the \ref reserveNode function.

     void reserveEdge(int n) { edges.reserve(n); };