The example implementations for DFS and BFS show calls to functions PreVisit and PostVisit. Better is to implement BFS and DFS using the visitor design pattern, with the visitor functions being passed...

The example implementations for DFS and BFS show calls to functions PreVisit and PostVisit. Better is to implement BFS and DFS using the visitor design pattern, with the visitor functions being passed in as either function or template parameters. Reimplement the BFS and DFS functions to make use of the visitor design pattern.