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