all_pairs_lowest_common_ancestor(G, pairs=None)[source]

Compute the lowest common ancestor for pairs of nodes.

GNetworkX directed graph
pairsiterable of pairs of nodes, optional (default: all pairs)

The pairs of nodes of interest. If None, will find the LCA of all pairs of nodes.

An iterator over ((node1, node2), lca) where (node1, node2) are
the pairs specified and lca is a lowest common ancestor of the pair.
Note that for the default of all pairs in G, we consider
unordered pairs, e.g. you will not get both (b, a) and (a, b).


Only defined on non-null directed acyclic graphs.

Uses the \(O(n^3)\) ancestor-list algorithm from: M. A. Bender, M. Farach-Colton, G. Pemmasani, S. Skiena, P. Sumazin. “Lowest common ancestors in trees and directed acyclic graphs.” Journal of Algorithms, 57(2): 75-94, 2005.