Reformat directed_graph.h.
Reformat directed_graph.h.

amanmehara/programming-app-data,amanmehara/programming-app-data,amanmehara/programming-app-data,amanmehara/programming-app-data,amanmehara/programming-app-data,amanmehara/programming-app-data,amanmehara/programming-app-data,amanmehara/programming-app-data