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_sequence : list or iterable container

A sequence of integer node in-degrees

out_sequence : list or iterable container

A sequence of integer node out-degrees

Returns :

valid : bool

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

Notes

This algorithm is from Kleitman and Wang [R241]. The worst case runtime is O(s * log n) where s and n are the sum and length of the sequences respectively.

References

[R241]

(1, 2) 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)