Write the A* Search Stub

In this exercise, you will modify route_planner.h, route_planner.cpp, main.cpp, and render.cpp to add a method AStarSearch, which will eventually become the search from start_node to end_node. In this exercise, you will only implement a basic version that returns a direct path between those two nodes. When you are done with this exercise, running the code should render a map with a direct path between the start and end nodes.

## To complete this exercise:

1. Add a AStarSearch declaration to the RoutePlanner class in route_planner.h. This method will be called from main.cpp, so it must be a public method. AStarSearch will use the start_node and end_node class variables, and it will modify the m_Model class variable, so it does not need any arguments, and should have void return type.
2. In route_planner.cpp define the AStarSearch method. The method should do the following:
   1. Set the parent of end_node to the start_node.
   2. Set m_Model.path to the result of calling ConstructFinalPath on end_node.
3. In main.cpp call AStarSearch on the RoutePlanner object. This should happen just after the RoutePlanner object is defined, but before the Render render{model}.
4. Also in main.cpp use the GetDistance() method of the RoutePlanner object to print the length of the path.
5. Uncomment the following lines in the Render::Display method in render.cpp. These lines will include the path in the rendered map:

    // DrawPath(surface);
    // DrawStartPosition(surface);   
    // DrawEndPosition(surface);

Solution