如何访问 Vertex 对象内的邻接表?
How can I access to adjacency lists inside the Vertex object?
我在 Python 中基于 Vertex 和图 classes 构建了一个图,但是在 isCycleUtil()
方法中,当我尝试通过 [=13= 访问 Vertex 对象时],我得到一个 TypeError: Vertex object not iterable。
你能帮我修复它并有一个可用的 isCycleUtil 方法吗?
class Vertex:
def __init__(self, node):
self.id = node
self.adjacent = {}
def __str__(self):
return str(self.id) + ' adjacent: ' + str([x.id for x in self.adjacent])
def add_neighbor(self, neighbor, weight=0):
self.adjacent[neighbor] = weight
def get_connections(self):
return self.adjacent.keys()
def get_id(self):
return self.id
def get_weight(self, neighbor):
return self.adjacent[neighbor]
def set_weight(self, neighbor, newvalue):
self.adjacent[neighbor] = newvalue
和图表 class:
class Graph:
def __init__(self):
self.vert_dict = {}
self.num_vertices = 0
def __iter__(self):
return iter(self.vert_dict.values())
def add_vertex(self, node):
self.num_vertices += 1
new_vertex = Vertex(node)
self.vert_dict[node] = new_vertex
return new_vertex
def get_vertex(self, n):
if n in self.vert_dict:
return self.vert_dict[n]
else:
return None
def add_edge(self, frm, to, cost = 0):
if frm not in self.vert_dict:
self.add_vertex(frm)
if to not in self.vert_dict:
self.add_vertex(to)
self.vert_dict[frm].add_neighbor(self.vert_dict[to], cost)
def get_vertices(self):
return self.vert_dict.keys()
def isCyclicUtil(self,v,visited,parent):
#Mark the current node as visited
if not visited[v]:
visited[v]= True
parent[v] = True
#Recur for all the vertices adjacent to this vertex
for i in self.vert_dict[v]:
# If the node is not visited then recurse on it
if (not visited[i] and self.isCyclicUtil(i,visited,parent)):
return True
elif (not parent[i]):
return True
parent[v] = False
return False
#Returns true if the graph contains a cycle, else false.
def isCyclic(self):
# Mark all the vertices as not visited
visited = {}
parent = {}
for i in self.vert_dict:
visited[i] = False
parent[i] = False
# Call the recursive helper function to detect cycle in different
#DFS trees
for i in self.vert_dict:
if(self.isCyclicUtil(i,visited,parent)):
return True
return False
为避免此错误,您需要替换:
for i in self.vert_dict[v]
和
for i in self.vert_dict[v].get_connections()
并使用:
visited[v.get_id()]
而不是
visited[v]
避免KeyError
您的图表是定向的,因此本主题中描述了正确的算法:
How to detect if a directed graph is cyclic?
您需要更改 isCyclicuntil 方法的实现:
def isCyclicUtil(self, v, visited, parent):
# Mark the current node as visited
if not visited[v]:
visited[v] = True
# Recur for all the vertices adjacent to this vertex
for i in self.vert_dict[v].get_connections():
# If the node is not visited then recurse on it
if visited[i.get_id()]:
return True
elif self.isCyclicUtil(i.get_id(), visited, parent):
return True
return False
我在 Python 中基于 Vertex 和图 classes 构建了一个图,但是在 isCycleUtil()
方法中,当我尝试通过 [=13= 访问 Vertex 对象时],我得到一个 TypeError: Vertex object not iterable。
你能帮我修复它并有一个可用的 isCycleUtil 方法吗?
class Vertex:
def __init__(self, node):
self.id = node
self.adjacent = {}
def __str__(self):
return str(self.id) + ' adjacent: ' + str([x.id for x in self.adjacent])
def add_neighbor(self, neighbor, weight=0):
self.adjacent[neighbor] = weight
def get_connections(self):
return self.adjacent.keys()
def get_id(self):
return self.id
def get_weight(self, neighbor):
return self.adjacent[neighbor]
def set_weight(self, neighbor, newvalue):
self.adjacent[neighbor] = newvalue
和图表 class:
class Graph:
def __init__(self):
self.vert_dict = {}
self.num_vertices = 0
def __iter__(self):
return iter(self.vert_dict.values())
def add_vertex(self, node):
self.num_vertices += 1
new_vertex = Vertex(node)
self.vert_dict[node] = new_vertex
return new_vertex
def get_vertex(self, n):
if n in self.vert_dict:
return self.vert_dict[n]
else:
return None
def add_edge(self, frm, to, cost = 0):
if frm not in self.vert_dict:
self.add_vertex(frm)
if to not in self.vert_dict:
self.add_vertex(to)
self.vert_dict[frm].add_neighbor(self.vert_dict[to], cost)
def get_vertices(self):
return self.vert_dict.keys()
def isCyclicUtil(self,v,visited,parent):
#Mark the current node as visited
if not visited[v]:
visited[v]= True
parent[v] = True
#Recur for all the vertices adjacent to this vertex
for i in self.vert_dict[v]:
# If the node is not visited then recurse on it
if (not visited[i] and self.isCyclicUtil(i,visited,parent)):
return True
elif (not parent[i]):
return True
parent[v] = False
return False
#Returns true if the graph contains a cycle, else false.
def isCyclic(self):
# Mark all the vertices as not visited
visited = {}
parent = {}
for i in self.vert_dict:
visited[i] = False
parent[i] = False
# Call the recursive helper function to detect cycle in different
#DFS trees
for i in self.vert_dict:
if(self.isCyclicUtil(i,visited,parent)):
return True
return False
为避免此错误,您需要替换:
for i in self.vert_dict[v]
和
for i in self.vert_dict[v].get_connections()
并使用:
visited[v.get_id()]
而不是
visited[v]
避免KeyError
您的图表是定向的,因此本主题中描述了正确的算法:
How to detect if a directed graph is cyclic?
您需要更改 isCyclicuntil 方法的实现:
def isCyclicUtil(self, v, visited, parent):
# Mark the current node as visited
if not visited[v]:
visited[v] = True
# Recur for all the vertices adjacent to this vertex
for i in self.vert_dict[v].get_connections():
# If the node is not visited then recurse on it
if visited[i.get_id()]:
return True
elif self.isCyclicUtil(i.get_id(), visited, parent):
return True
return False