original graph:
0 --> 2 
1 --> 1 3 4 
2 --> 1 3 4 
3 --> 1 4 
4 --> 0 1 

reversed graph:
0 --> 4 
1 --> 1 2 3 4 
2 --> 0 
3 --> 1 2 
4 --> 1 2 3