# is_digraphical#

is_digraphical(in_sequence, out_sequence)[source]#

Returns True if some directed graph can realize the in- and out-degree sequences.

Parameters:
in_sequencelist or iterable container

A sequence of integer node in-degrees

out_sequencelist or iterable container

A sequence of integer node out-degrees

Returns:
validbool

True if in and out-sequences are digraphic False if not.

Notes

This algorithm is from Kleitman and Wang [1]. The worst case runtime is $$O(s \times \log n)$$ where $$s$$ and $$n$$ are the sum and length of the sequences respectively.

References

[1]

D.J. Kleitman and D.L. Wang Algorithms for Constructing Graphs and Digraphs with Given Valences and Factors, Discrete Mathematics, 6(1), pp. 79-88 (1973)