[英]Find path from a list of tuples in Python
我有以下形式的元组列表:
data = [('Abe', 'Bob', '3'),
('Abe', 'Frank', '5'),
('Abe', 'George', '4'),
('Carl', 'Bob', '1'),
('Dan', 'Carl', '2')]
此数据模拟无向图,其中从'Abe'到大小为3的'Bob'之间存在联系。由于该图是无向的,因此也意味着从'Bob'到大小为3的'Abe'之间存在联系。好。
我需要显示两个输入之间是否存在连接及其权重。 例如,如果输入为“ Abe”,“ Dan”,则结果将返回从“ Abe”到“ Dan”的最短(最小节点跳,不是最不重要的权重)路径,即Abe,Bob,Carl,Dan和权重3 + 1 + 2 = 6。
我有这段代码显示“ Abe”是否会到达“ Dan”,但是我不知道如何返回路径。
def get_path_and_weight(data, start, end):
reachable = [start]
added = -1
while added != 0:
added = 0
for first, second, weight in data:
if(first in reachable) and (second not in reachable):
reachable.append(second)
added += 1
if(first not in reachable) and (second in reachable):
reachable.append(first)
added += 1
if (end in reachable):
print("YES")
#return path
else:
print("NO")
有许多已经开发和调试过的软件包可以做到这一点,例如, networkx
import networkx as nx
data = [('Abe', 'Bob', '3'),
('Abe', 'Frank', '5'),
('Abe', 'George', '4'),
('Carl', 'Bob', '1'),
('Dan', 'Carl', '2')]
g = nx.Graph()
for e in data:
g.add_edge(e[0], e[1], distance=int(e[2]))
>>> nx.shortest_path(g, 'Abe', 'Bob', 'distance'), nx.shortest_path_length(g, 'Abe', 'Bob', 'distance')
(['Abe', 'Bob'], 3)
您可以生成所有可能的路径,然后按权重对它们进行排序。 注意我已经将数据中的权重更改为数字,而不是字符串:
data = [
('Abe', 'Bob', 3),
('Abe', 'Frank', 5),
('Abe', 'George', 4),
('Carl', 'Bob', 1),
('Dan', 'Carl', 2),
]
WEIGHT = 0
NODES = slice(1, None)
def get_path_and_weight(data, start, end):
paths = [[0, start]]
added = True
while added:
added = False
for first, second, weight in data:
for path in paths:
candidate = None
if (first in path[NODES]) and (second not in path[NODES]):
candidate = second
elif (first not in path[NODES]) and (second in path[NODES]):
candidate = first
if candidate:
new_path = list(path)
new_path.append(candidate)
new_path[WEIGHT] += weight
if new_path not in paths:
paths.append(new_path)
added = True
for path in sorted(paths):
if end in path[NODES]:
return path
return None
然后,您可以将其称为:
weight, *path = get_path_and_weight(data, "Abe", "Dan")
print(path, "with weight", weight)
给出结果:
['Abe', 'Bob', 'Carl', 'Dan'] with weight 6
并且由于它返回路径或None
,因此您仍然可以将其用作谓词函数:
if get_path_and_weight(data, "Abe", "Dan"):
print("connected")
def get_rpath_with_weight(data,start,end):
rpath = []
reachable=False
nxt_dst = start
weight_ = 0
rpath.append(nxt_dst)
for datum in data:
if nxt_dst in datum:
#print datum
fm_ = datum[0]
to_ = datum[1]
weight_ = weight_ + int(datum[2])
if fm_ == nxt_dst:
nxt_dst = to_
else:
nxt_dst = fm_
if nxt_dst == end:
reachable=True
rpath.append(nxt_dst)
print rpath,weight_,reachable
get_rpath_with_weight(data,'Abe','Dan')
get_rpath_with_weight(data,'Dan','Frank')
样本输出
['Abe', 'Bob', 'Carl', 'Dan'] 6 True
['Dan', 'Carl'] 2 False
上面的示例可以获取路径并确定是否可访问,但是我认为您也需要进一步增强它以处理多个路径。
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