力扣刷题(python)50天——第四十四天:二叉搜索树的最近公共祖先
题目描述
来源:力扣(LeetCode)
链接:https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
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方法
拿到题后感觉虽然做了很多题了,有很多想法,但是还是没有想出解法,参考:
https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree/solution/er-cha-sou-suo-shu-de-zui-jin-gong-gong-zu-xian–2/
后发现,之前二叉搜索树的性质我没有理解透彻,二叉搜索树的大于小于对于左右树枝是永久性的。
解答
# Definition for a binary tree node.
# class TreeNode(object):
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution(object):
def lowestCommonAncestor(self, root, p, q):
"""
:type root: TreeNode
:type p: TreeNode
:type q: TreeNode
:rtype: TreeNode
"""
root_val=root.val
p_val=p.val
q_val=q.val
if p_val>root_val and q_val>root_val:
self.lowestCommonAncestor(root.right, p, q)
elif p_val<root_val and q_val<root_val:
self.lowestCommonAncestor(root.left, p, q)
else:
self.ans=root
return self.ans