Function maxRecursionDepth 已达到，即使在添加访问过的字典之后

Question

这是问题：

我的代码是：

count = 0
visited = {}

def BackAndForth(AList,end1,end2):
  global count
  global visited

  for i in AList.keys():
    visited[i] = False
  print(AList[end1])
  visited[end1] = True
  if(end2 in AList[end1]):
    count+=1
  for i in AList[end1]:
    if(i!=end2 and not visited[i]):
      visited[i] = True
      BackAndForth(AList,i,end2)

  return count

Alist = {
    0 :[2,3,6],
    1 :[3,5,6] ,
    2 :[0,3,4],
    3 :[0,1,2,4],
    4 :[2,3,5],
    5 :[1,4,6],
    6 :[0,1,5],
}
end1=0
end2=1
print(BackAndForth(Alist,end1,end2))

即使我添加了一个访问过的字典，这个 function 也会无限重复。

Answer 1

您在递归方法的开头将visited的字典设置为False ：

for i in AList.keys():
    visited[i] = False

这将在每次调用时重置访问列表，从而重新开始。

相反，使用None作为默认参数，只初始化访问列表一次并将其传递给递归调用：

def BackAndForth(AList, end1, end2, visited=None):
    global count
    if visited is None:
        visited = {}
        for i in AList.keys():
            visited[i] = False
    [...]