chore: import upstream snapshot with attribution

2026-07-13 12:36:30 +08:00
commit 55ab4e4a73
473 changed files with 72932 additions and 0 deletions
@@ -0,0 +1,160 @@
+from easygraph.utils.decorators import *
+
+
+__all__ = [
+    "is_connected",
+    "number_connected_components",
+    "connected_components",
+    "connected_components_directed",
+    "connected_component_of_node",
+]
+
+
+@not_implemented_for("multigraph")
+def is_connected(G):
+    """Returns whether the graph is connected or not.
+
+    Parameters
+    ----------
+    G : easygraph.Graph or easygraph.DiGraph
+
+    Returns
+    -------
+    is_biconnected : boolean
+        `True` if the graph is connected.
+
+    Examples
+    --------
+
+    >>> is_connected(G)
+
+    """
+    assert len(G) != 0, "No node in the graph."
+    arbitrary_node = next(iter(G))  # Pick an arbitrary node to run BFS
+    return len(G) == sum(1 for node in _plain_bfs(G, arbitrary_node))
+
+
+@not_implemented_for("multigraph")
+def number_connected_components(G):
+    """Returns the number of connected components.
+
+    Parameters
+    ----------
+    G : easygraph.Graph
+
+    Returns
+    -------
+    number_connected_components : int
+        The number of connected components.
+
+    Examples
+    --------
+    >>> number_connected_components(G)
+
+    """
+    return sum(1 for component in _generator_connected_components(G))
+
+
+@not_implemented_for("multigraph")
+@hybrid("cpp_connected_components_undirected")
+def connected_components(G):
+    """Returns a list of connected components, each of which denotes the edges set of a connected component.
+
+    Parameters
+    ----------
+    G : easygraph.Graph
+    Returns
+    -------
+    connected_components : list of list
+        Each element list is the edges set of a connected component.
+
+    Examples
+    --------
+    >>> connected_components(G)
+
+    """
+    seen = set()
+    for v in G:
+        if v not in seen:
+            c = set(_plain_bfs(G, v))
+            seen.update(c)
+            yield c
+
+
+@not_implemented_for("multigraph")
+@hybrid("cpp_connected_components_directed")
+def connected_components_directed(G):
+    """Returns a list of connected components, each of which denotes the edges set of a connected component.
+
+    Parameters
+    ----------
+    G :  easygraph.DiGraph
+    Returns
+    -------
+    connected_components : list of list
+        Each element list is the edges set of a connected component.
+
+    Examples
+    --------
+    >>> connected_components(G)
+
+    """
+    seen = set()
+    for v in G:
+        if v not in seen:
+            c = set(_plain_bfs(G, v))
+            seen.update(c)
+            yield c
+
+
+def _generator_connected_components(G):
+    seen = set()
+    for v in G:
+        if v not in seen:
+            component = set(_plain_bfs(G, v))
+            yield component
+            seen.update(component)
+
+
+@not_implemented_for("multigraph")
+def connected_component_of_node(G, node):
+    """Returns the connected component that *node* belongs to.
+
+    Parameters
+    ----------
+    G : easygraph.Graph
+
+    node : object
+        The target node
+
+    Returns
+    -------
+    connected_component_of_node : set
+        The connected component that *node* belongs to.
+
+    Examples
+    --------
+    Returns the connected component of one node `Jack`.
+
+    >>> connected_component_of_node(G, node='Jack')
+
+    """
+    return set(_plain_bfs(G, node))
+
+
+@hybrid("cpp_plain_bfs")
+def _plain_bfs(G, source):
+    """
+    A fast BFS node generator
+    """
+    G_adj = G.adj
+    seen = set()
+    nextlevel = {source}
+    while nextlevel:
+        thislevel = nextlevel
+        nextlevel = set()
+        for v in thislevel:
+            if v not in seen:
+                yield v
+                seen.add(v)
+                nextlevel.update(G_adj[v])