Note

This documents the development version of NetworkX. Documentation for the current release can be found here.

# networkx.algorithms.lowest_common_ancestors.lowest_common_ancestor¶

lowest_common_ancestor(G, node1, node2, default=None)[source]

Compute the lowest common ancestor of the given pair of nodes.

Parameters
• G (NetworkX directed graph)

• node1, node2 (nodes in the graph.)

• default (object) – Returned if no common ancestor between node1 and node2

Returns

• The lowest common ancestor of node1 and node2,

• or default if they have no common ancestors.

Notes

Only defined on non-null directed acyclic graphs. Takes n log(n) time in the size of the graph. See all_pairs_lowest_common_ancestor when you have more than one pair of nodes of interest.