leetcode 226. 翻转二叉树（C++、python）

翻转一棵二叉树。

示例：

输入：

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

输出：

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

C++

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) 
    {
        if(NULL==root)
        {
            return NULL;
        }
        TreeNode* p=invertTree(root->left);
        TreeNode* q=invertTree(root->right);
        root->left=q;
        root->right=p;
        return root;
    }
};

python

# 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: TreeNode) -> TreeNode:
        if None==root:
            return None
        p=self.invertTree(root.left)
        q=self.invertTree(root.right)
        root.left=q
        root.right=p
        return root