在一个类内调用递归函数。

huangapple
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英文:

Calling a recursive function inside a class

问题

  1.     def apend(self, arr, target):
  2.         """arr是从根节点到目标节点的路径列表，self是根节点"""
  4.         if self is None:
  5.             return False
  6.         arr.append(self.data)
  7.         if self.data == target:
  8.             return True
  9.         if self.left and self.left.apend(arr, target) or (self.right and self.right.apend(arr, target)):
  10.             return True
  11.         arr.pop()
  12.         return False
英文:

I am trying to call a recursive method in order to find path from root to node in a binary tree. There are few solns. for this problem on the internet, but I am trying to use slightly different approach by implementing a method inside a Node class.

Here is my logic for the soln.

  1.     def apend(self, arr, target):
  2.         """ arr is the list which has the path from root to target node, self is the root """
  3.     
  4.  
  5.         if self is None:
  6.             return False
  7.         arr.append(self.data)
  8.         if self.data==target:
  9.             return True
  10.         if self.left.apend(arr, target) or self.right.apend(arr, target):
  11.             return True
  12.         arr.pop()
  13.         return False

I a perfectly okay with how this logic is working, means if the target is found in either right or left subtree return True.

My question is; what if self is a leaf node, i.e. self.left is None. same with self. right. In that case the recursive call is giving an error.
Can I get some help on how to rectify that situation? thanx

答案1

得分: 2

你需要检查 self 是否为 None，而应该在进行递归调用之前检查 self.left 或 self.right 是否为 None。

英文:

Instead of checking if self is None you need to check if self.left or self.right is None before you make a recursive call.

  1. def apend(self, arr, target):
  2.     """ arr is the list which has the path from root to target node, self is the root """
  5.     arr.append(self.data)
  6.     if self.data==target:
  7.         return True
  8.     if self.left is not None and self.left.apend(arr, target):
  9.         return True
  10.     if self.right is not None and self.right.apend(arr, target):
  11.         return True
  12.     arr.pop()
  13.     return False

huangapple
  • 本文由 发表于 2023年2月19日 16:44:30
  • 转载请务必保留本文链接：https://go.coder-hub.com/75498943.html
  • python
  • recursion
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