4.1.3 Create a copy constructor for Graph that
takes as input a graph G and creates and initializes
a new copy of the graph. Any changes a client makes to G
should not affect the newly created graph.
-----------------------original-------------------------------
13 vertices, 13 edges
0: 6 2 1 5
1: 0
2: 0
3: 5 4
4: 5 6 3
5: 3 4 0
6: 0 4
7: 8
8: 7
9: 11 10 12
10: 9
11: 9 12
12: 11 9
-----------------------copy-------------------------------
13 vertices, 13 edges
0: 6 2 1 5
1: 0
2: 0
3: 5 4
4: 5 6 3
5: 3 4 0
6: 0 4
7: 8
8: 7
9: 11 10 12
10: 9
11: 9 12
12: 11 9