is_pseudographical

is_pseudographical(sequence)

Returns True if some pseudograph can realize the sequence.

Every nonnegative integer sequence with an even sum is pseudographical (see [R224]).

Parameters :

sequence : list or iterable container

A sequence of integer node degrees

Returns :

valid : bool

True if the sequence is a pseudographic degree sequence and False if not.

Notes

The worst-case run time is O(n) where n is the length of the sequence.

References

[R224]

(1, 2) F. Boesch and F. Harary. “Line removal algorithms for graphs and their degree lists”, IEEE Trans. Circuits and Systems, CAS-23(12), pp. 778-782 (1976).