Graph encoding schemes:

Adjacency list: Below we represent a graph of 6 nodes with an adjacency list.

1       → 2       → 4/
2       → 5/              
3       → 6       → 5/
4       → 2/              
5       → 4/              
6       → 6/              

Adjacency matrix: Below we reperesent the same graph of 6 nodes with an adjacency matrix.

        1       2       3       4       5       6
1       0       1       0       1       0       0
2       0       0       0       0       1       0
3       0       0       0       0       1       1
4       0       1       0       0       0       0
5       0       0       0       1       0       0
6       0       0       0       0       0       1