LeetCode Invert Binary Tree

Problem

Invert a binary tree.

Example:

Input:

     4
   /   \
  2     7
 / \   / \
1   3 6   9
Output:

     4
   /   \
  7     2
 / \   / \
9   6 3   1

对树进行完全的左右节点交换

Python3

# Invert a binary tree.
#
# Example:
#
# Input:
#
#      4
#    /   \
#   2     7
#  / \   / \
# 1   3 6   9
# Output:
#
#      4
#    /   \
#   7     2
#  / \   / \
# 9   6 3   1

# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None

class Solution:
    def invertTree(self, root):
        """
        :type root: TreeNode
        :rtype: TreeNode
        """
        if not root:
            return
        root.left,root.right = root.right,root.left
        self.invertTree(root.left)
        self.invertTree(root.right)
        return root

分析

很自然的想到了递归