为了练习,我正在做2015年的编程挑战活动“Advent of Code”,目前卡在第9天。目标是找到最短距离,同时确保每个位置只访问一次。每个点直接连接到其他点,起点和终点必须不同。我已经提出了一个解决方案,但最终值不正确,我没有看到潜在的问题。
首先,我创建了一个包含位置和距离的图形对象。然后,我将每个位置的排列收集到一个列表中,再找到并总结每个排列的距离。最后,我打印出最小距离值,这是练习的解决方案。
代码如下:
首先,我创建了一个包含位置和距离的图形对象。然后,我将每个位置的排列收集到一个列表中,再找到并总结每个排列的距离。最后,我打印出最小距离值,这是练习的解决方案。
代码如下:
from collections import defaultdict
from itertools import permutations
with open("input.txt") as file:
input_ = file.read().split("\n")[:-1]
class Graph():
def __init__(self):
self.edges = defaultdict(list)
self.weights = {}
def add_edge(self, from_node, to_node, weight):
self.edges[from_node].append(to_node)
self.edges[to_node].append(from_node)
self.weights[(from_node, to_node)] = weight
self.weights[(to_node, from_node)] = weight
graph = Graph()
edges = [(i.split()[0], i.split()[2], int(i.split()[-1])) for i in input_]
for edge in edges:
graph.add_edge(*edge)
loc_set = set([i[0] for i in edges])
routes = list(permutations(loc_set, len(loc_set)))
dists = []
for i in routes:
print(i)
dist_temp = []
for k in range(len(i))[1:]:
dist_temp.append(graph.weights[(i[k-1], i[k])])
dists.append(sum(dist_temp))
print(dist_temp)
print(sum(dist_temp))
print(min(dists))
在获取无效值后,我手动检查了一些排列及其对应的距离,因此代码中有打印内容。
输入(将其复制并粘贴到记事本中,并将其保存为input.txt,应该可以正常工作):
Faerun to Tristram = 65
Faerun to Tambi = 129
Faerun to Norrath = 144
Faerun to Snowdin = 71
Faerun to Straylight = 137
Faerun to AlphaCentauri = 3
Faerun to Arbre = 149
Tristram to Tambi = 63
Tristram to Norrath = 4
Tristram to Snowdin = 105
Tristram to Straylight = 125
Tristram to AlphaCentauri = 55
Tristram to Arbre = 14
Tambi to Norrath = 68
Tambi to Snowdin = 52
Tambi to Straylight = 65
Tambi to AlphaCentauri = 22
Tambi to Arbre = 143
Norrath to Snowdin = 8
Norrath to Straylight = 23
Norrath to AlphaCentauri = 136
Norrath to Arbre = 115
Snowdin to Straylight = 101
Snowdin to AlphaCentauri = 84
Snowdin to Arbre = 96
Straylight to AlphaCentauri = 107
Straylight to Arbre = 14
AlphaCentauri to Arbre = 46
我相信在这个问题上有更加精细的解决方案,因为我只是一个业余爱好者,所以我很乐意听取建议。然而,如果我们能够找出我的方法存在的缺陷并使其正常工作,我会非常高兴。