题目描述

blablabla

样例

blablabla

算法1

() $O(n^2)$

blablabla

时间复杂度分析：blablabla

Python 代码

# 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 convert(self, root):
        """
        :type root: TreeNode
        :rtype: TreeNode
        """
        if not root:
            return
        self.res = []
        self.pre_order(root)
        for i, node in enumerate(self.res[:-1]):
            node.right = self.res[i + 1]
            self.res[i + 1].left = node
        return self.res[0]

    def pre_order(self, root):
        if not root:
            return
        self.pre_order(root.left)
        self.res.append(root)
        self.pre_order(root.right)