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 [1]).

Parameters:

sequencelist or iterable container

A sequence of integer node degrees

Returns:

validbool

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

[1]

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).