// Shiyu's code
public UndirectedGraph <TVertex, TEdge> Clone()
{
var g = new UndirectedGraph <TVertex, TEdge>(this.allowParallelEdges);
var nodes = this.adjacentEdges.Keys;
foreach (var n in nodes)
{
g.AddVertex(n);
}
var edgesList = this.adjacentEdges.Values;
foreach (var edges in edgesList)
{
foreach (var e in edges)
{
g.AddEdge(e);
}
}
return(g);
}
