235 lowest common ancestor of a binary search tree
235. Lowest Common Ancestor of a Binary Search Tree
题目： https://leetcode.com/problems/lowest-common-ancestor-of-a-binary-search-tree/
难度 : Easy
- 两个node，一个大于root，一个小于root，那么必定root两边，共同的ancestor是root，同时再考虑同为空的状况
- 两个node，都比node小，到左边去寻找，那么先找到那个必定是common ancestor
- 两个node，都比node大，类似....
AC解法
class Solution(object):
def lowestCommonAncestor(self, root, p, q):
"""
:type root: TreeNode
:type p: TreeNode
:type q: TreeNode
:rtype: TreeNode
"""
if root == None or root == p or root == q:
return root
elif p.val < root.val < q.val or q.val < root.val < p.val :
return root
elif p.val < root.val and q.val < root.val:
return self.lowestCommonAncestor(root.left,p,q)
else:
return self.lowestCommonAncestor(root.right,p,q)
