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b431e9b684
Python 2 had old style and new style classes. Python 3 has only new style classes. There is no point to subclass from object any more. See: https://pagure.io/freeipa/issue/7715 Signed-off-by: Christian Heimes <cheimes@redhat.com> Reviewed-By: Florence Blanc-Renaud <frenaud@redhat.com>
89 lines
2.4 KiB
Python
89 lines
2.4 KiB
Python
#
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# Copyright (C) 2015-2017 FreeIPA Contributors see COPYING for license
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#
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from collections import deque
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class Graph:
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"""
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Simple oriented graph structure
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G = (V, E) where G is graph, V set of vertices and E list of edges.
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E = (tail, head) where tail and head are vertices
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"""
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def __init__(self):
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self.vertices = set()
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self.edges = []
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self._adj = dict()
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def add_vertex(self, vertex):
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self.vertices.add(vertex)
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self._adj[vertex] = []
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def add_edge(self, tail, head):
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if tail not in self.vertices:
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raise ValueError("tail is not a vertex")
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if head not in self.vertices:
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raise ValueError("head is not a vertex")
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self.edges.append((tail, head))
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self._adj[tail].append(head)
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def remove_edge(self, tail, head):
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try:
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self.edges.remove((tail, head))
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except KeyError:
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raise ValueError(
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"graph does not contain edge: ({0}, {1})".format(tail, head)
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)
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self._adj[tail].remove(head)
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def remove_vertex(self, vertex):
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try:
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self.vertices.remove(vertex)
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except KeyError:
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raise ValueError(
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"graph does not contain vertex: {0}".format(vertex)
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)
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# delete _adjacencies
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del self._adj[vertex]
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for adj in self._adj.values():
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adj[:] = [v for v in adj if v != vertex]
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# delete edges
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self.edges = [
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e for e in self.edges if vertex not in (e[0], e[1])
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]
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def get_tails(self, head):
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"""
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Get list of vertices where a vertex is on the right side of an edge
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"""
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return [e[0] for e in self.edges if e[1] == head]
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def get_heads(self, tail):
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"""
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Get list of vertices where a vertex is on the left side of an edge
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"""
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return [e[1] for e in self.edges if e[0] == tail]
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def bfs(self, start=None):
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"""
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Breadth-first search traversal of the graph from `start` vertex.
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Return a set of all visited vertices
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"""
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if not start:
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start = next(iter(self.vertices))
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visited = set()
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queue = deque([start])
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while queue:
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vertex = queue.popleft()
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if vertex not in visited:
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visited.add(vertex)
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queue.extend(set(self._adj.get(vertex, [])) - visited)
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return visited
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