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Diffstat (limited to '.venv/lib/python3.12/site-packages/networkx/algorithms/components/connected.py')
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diff --git a/.venv/lib/python3.12/site-packages/networkx/algorithms/components/connected.py b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/connected.py new file mode 100644 index 00000000..ebe0d8c1 --- /dev/null +++ b/.venv/lib/python3.12/site-packages/networkx/algorithms/components/connected.py @@ -0,0 +1,216 @@ +"""Connected components.""" + +import networkx as nx +from networkx.utils.decorators import not_implemented_for + +from ...utils import arbitrary_element + +__all__ = [ + "number_connected_components", + "connected_components", + "is_connected", + "node_connected_component", +] + + +@not_implemented_for("directed") +@nx._dispatchable +def connected_components(G): + """Generate connected components. + + Parameters + ---------- + G : NetworkX graph + An undirected graph + + Returns + ------- + comp : generator of sets + A generator of sets of nodes, one for each component of G. + + Raises + ------ + NetworkXNotImplemented + If G is directed. + + Examples + -------- + Generate a sorted list of connected components, largest first. + + >>> G = nx.path_graph(4) + >>> nx.add_path(G, [10, 11, 12]) + >>> [len(c) for c in sorted(nx.connected_components(G), key=len, reverse=True)] + [4, 3] + + If you only want the largest connected component, it's more + efficient to use max instead of sort. + + >>> largest_cc = max(nx.connected_components(G), key=len) + + To create the induced subgraph of each component use: + + >>> S = [G.subgraph(c).copy() for c in nx.connected_components(G)] + + See Also + -------- + strongly_connected_components + weakly_connected_components + + Notes + ----- + For undirected graphs only. + + """ + seen = set() + n = len(G) + for v in G: + if v not in seen: + c = _plain_bfs(G, n, v) + seen.update(c) + yield c + + +@not_implemented_for("directed") +@nx._dispatchable +def number_connected_components(G): + """Returns the number of connected components. + + Parameters + ---------- + G : NetworkX graph + An undirected graph. + + Returns + ------- + n : integer + Number of connected components + + Raises + ------ + NetworkXNotImplemented + If G is directed. + + Examples + -------- + >>> G = nx.Graph([(0, 1), (1, 2), (5, 6), (3, 4)]) + >>> nx.number_connected_components(G) + 3 + + See Also + -------- + connected_components + number_weakly_connected_components + number_strongly_connected_components + + Notes + ----- + For undirected graphs only. + + """ + return sum(1 for cc in connected_components(G)) + + +@not_implemented_for("directed") +@nx._dispatchable +def is_connected(G): + """Returns True if the graph is connected, False otherwise. + + Parameters + ---------- + G : NetworkX Graph + An undirected graph. + + Returns + ------- + connected : bool + True if the graph is connected, false otherwise. + + Raises + ------ + NetworkXNotImplemented + If G is directed. + + Examples + -------- + >>> G = nx.path_graph(4) + >>> print(nx.is_connected(G)) + True + + See Also + -------- + is_strongly_connected + is_weakly_connected + is_semiconnected + is_biconnected + connected_components + + Notes + ----- + For undirected graphs only. + + """ + n = len(G) + if n == 0: + raise nx.NetworkXPointlessConcept( + "Connectivity is undefined for the null graph." + ) + return sum(1 for node in _plain_bfs(G, n, arbitrary_element(G))) == len(G) + + +@not_implemented_for("directed") +@nx._dispatchable +def node_connected_component(G, n): + """Returns the set of nodes in the component of graph containing node n. + + Parameters + ---------- + G : NetworkX Graph + An undirected graph. + + n : node label + A node in G + + Returns + ------- + comp : set + A set of nodes in the component of G containing node n. + + Raises + ------ + NetworkXNotImplemented + If G is directed. + + Examples + -------- + >>> G = nx.Graph([(0, 1), (1, 2), (5, 6), (3, 4)]) + >>> nx.node_connected_component(G, 0) # nodes of component that contains node 0 + {0, 1, 2} + + See Also + -------- + connected_components + + Notes + ----- + For undirected graphs only. + + """ + return _plain_bfs(G, len(G), n) + + +def _plain_bfs(G, n, source): + """A fast BFS node generator""" + adj = G._adj + seen = {source} + nextlevel = [source] + while nextlevel: + thislevel = nextlevel + nextlevel = [] + for v in thislevel: + for w in adj[v]: + if w not in seen: + seen.add(w) + nextlevel.append(w) + if len(seen) == n: + return seen + return seen |