def traversal(g: Graph, end) -> list:
res = []
vertex = g.get_vertex(end)
while vertex:
res.append(vertex.id)
vertex = vertex.predecessor
return res
def bfs(g: Graph, start, end) -> int:
start_vertex = g.get_vertex(start)
end_vertex = g.get_vertex(end)
if start_vertex is None or end_vertex is None:
raise ValueError(f'{start}或{end}不在单词表中')
queue, found = Queue(), False
queue.enqueue(start_vertex)
while not queue.is_empty() and not found:
vertex: Vertex = queue.dequeue()
for neighbor in vertex.connect:
if neighbor.color == 'white':
neighbor.color = 'gray'
neighbor.predecessor = vertex
neighbor.distance = vertex.distance + vertex.get_weight(
neighbor)
queue.enqueue(neighbor)
# 找到目标时提前退出
# if neighbor is end_vertex:
# found = True
vertex.color = 'black'
return end_vertex.distance
def prim(g: Graph):
# 随机选择一个起始顶点
start_vertex = g.get_vertex(choice(g.get_all_vertex()))
# 初始化
init_graph(g)
start_vertex.distance = 0
queue = PriorityQueue()
vertex_list = [(vertex, vertex.distance) for vertex in g]
queue.build_queue(vertex_list)
while not queue.is_empty():
vertex: Vertex = queue.dequeue()
for neighbor in vertex.connect:
if neighbor not in queue:
continue
new_cost = vertex.get_weight(neighbor)
if new_cost < neighbor.distance:
neighbor.distance = new_cost
neighbor.predecessor = vertex
queue.update_priority(neighbor, new_cost)
def dijkstra(g: Graph, start) -> Vertex:
start_vertex = g.get_vertex(start)
if start_vertex is None:
raise ValueError(f'{start}点不存在')
# 初始化
init_graph(g)
start_vertex.distance = 0
queue = PriorityQueue()
vertex_list = [(vertex, vertex.distance) for vertex in g]
queue.build_queue(vertex_list)
while not queue.is_empty():
vertex: Vertex = queue.dequeue()
for neighbor in vertex.connect:
new_distance = vertex.distance + vertex.get_weight(neighbor)
if new_distance < neighbor.distance:
neighbor.distance = new_distance
neighbor.predecessor = vertex
queue.update_priority(neighbor, new_distance)
return start_vertex
g.add_edge('a', 'c', 3)
g.add_edge('c', 'f', 5)
g.add_edge('f', 'g', 1)
g.add_edge('b', 'e', 4)
g.add_edge('b', 'd', 1)
g.add_edge('b', 'c', 1)
g.add_edge('d', 'e', 1)
print 'Graph data:'
for v in g:
for w in v.get_connections():
vid = v.get_id()
wid = w.get_id()
print '( %s , %s, %3d)' % (vid, wid, v.get_weight(w))
prims(g, g.get_vertex('a'))
### floyd warshall algorithm for all vertex shortest path
from pythonds.graphs import Graph, Vertex
def floyd_Warshall(aGraph):
distmat = [[100 for x in range(0, aGraph.numVertices + 1)]
for y in range(0, aGraph.numVertices + 1)]
for row in distmat:
print row
for num in range(0, aGraph.numVertices + 1):
distmat[num][num] = 0
