<h3><a title="题目描述" href="https://leetcode-cn.com/problems/lowest-common-ancestor-of-a-binary-search-tree">题目描述</a></h3>
<h4>我的解法[递归]</h4>
```python
# Definition for a binary tree node.
# class TreeNode:
# def __init__(self, x):
# self.val = x
# self.left = None
# self.right = None
class Solution:
def lowestCommonAncestor(self, root, p, q):
parrent_val = root.val
p_val = p.val
q_val = q.val
if(p_val >parrent_val and q_val > parrent_val):
return self.lowestCommonAncestor(root.right,p,q)
#class: def function():return self.function
elif(p_val < parrent_val and q_val < parrent_val):
return self.lowestCommonAncestor(root.left,p,q)
else:
return root
```
<h4>迭代解法</h4>
```python
class Solution:
def lowestCommonAncestor(self, root, p, q):
p_val = p.val
q_val = q.val
node = root
while node:
parent_val = node.val
if p_val > parent_val and q_val > parent_val:
node = node.right
elif p_val < parent_val and q_val < parent_val:
node = node.left
else:
return node
```
#### Note
```python
class Solution:
def function(self,a,b,c):
# return function(a+1,b+1,c+1) 这种写法是错的
return self.function(a+1,b+1,c+1)
```
- 一开始看题目的时候没有注意是二叉搜索树的特性 浪费了时间
- 迭代的思路是**寻找到让p和q不在同一颗子树上的分割点,这个分割点就是公共祖先**
Leetcode235 二叉搜索树的最近公共祖先
