The maximum degree of each node is (n- 1), where n is the number of nodes.

such as

1, (0, 1, 1, 2,3) can form a simple undirected graph degree sequence.

2.(2, 3, 3, 4, 4, 5) cannot form a simple undirected graph degree sequence. (The number of odd-numbered nodes is 3, not even)

3.( 1, 3, 3, 3) cannot form a simple undirected graph degree sequence.

(2,2,4) cannot form a simple undirected graph degree sequence.