Path should be A-B-D-F
A B D F 

Path should be A-B-D-E
A B D E 

Path should be E
E 

Path should not exist


Path should be A-B
A B 

Path should not exist


Path should be D-E
D E 

Path should be B-D-F
B D F 

Path should be B-D-E
B D E 

Path should be D
D 

Path should be C
C 

