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is_tree

is_tree(G)

Returns \(True\) if \(G\) is a tree.

A tree is a connected graph with no undirected cycles.

For directed graphs, \(G\) is a tree if the underlying graph is a tree. The underlying graph is obtained by treating each directed edge as a single undirected edge in a multigraph.

Parameters:

G : graph

The graph to test.

Returns:

b : bool

A boolean that is \(True\) if \(G\) is a tree.

See also

is_arborescence

Notes

In another convention, a directed tree is known as a polytree and then tree corresponds to an arborescence.