Take this diagram as an example to list the degrees of each node:
If A is the adjacency matrix of a simple graph, then A n i.j represents the number of paths with length n from node I to node J, and the length of each edge of the graph is 1 (it sounds a little rough, let's give an example).
Then we draw the matrix A 2
In matrix A 2:
A 2 a, A means there are three paths with length 2 from node A to node A:
A2A and b indicate that there are 1 paths with length 2 from node A to node B:
A2A and c indicate that there are two paths with length 2 from node A to node C:
A 2 a, d indicates that there are 1 paths with length 2 from node A to node D:
The representation of the chart ends here. Thank you!