# 226.Invert Binary Tree

**226.Invert Binary Tree**

难度:Easy

> 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
```

备注: 这个问题是受到 Max Howell 的 原问题 启发的 ：

> 谷歌：我们90％的工程师使用您编写的软件(Homebrew)，但是您却无法在面试时在白板上写出翻转二叉树这道题，这太糟糕了。

代码如下：

```
/**
 * 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(!root) return NULL;
        root->right=invertTree(root->right);
        root->left=invertTree(root->left);
        TreeNode* tmp=root->right;
        root->right=root->left;
        root->left=NULL;
        root->left=tmp;
        return root;

    }
};
```


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