题目描述

blablabla

样例

# 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
        """
        if not root:
            return None
        if q == root or p == root: # 如果找到了某一个点 则当前节点为答案
            return root
        left = self.lowestCommonAncestor(root.left, p, q)
        right = self.lowestCommonAncestor(root.right, p, q)
        if left and right: # 如果左子树中可以找到其公共祖先 右子树也可以 则说明当前节点就是答案
            return root
        if not left: # 左边找不到了 那就是右子树的答案
            return right
        elif not right: # 右边亦然
            return left