Added code to prevent edges from crossing

graph.h

@@ -43,6 +43,8 @@ class Graph
     Vertex* get_current_vertex() { return current_vertex; }
 
  private:
+    bool vertex_would_overlap(int x, int y, int r);
+    bool crosses_edge(Edge e);
     void add_vertex(int x, int y, int r);
 
     Vertex* current_vertex;