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# 226. Invert Binary Tree

## [題目連結:] https://leetcode.com/problems/invert-binary-tree/description/

## 題目:
Given the ```root``` of a binary tree, invert the tree, and return its root.


## 解題想法:
* 此題為反轉一個二元樹
* 遞迴處理即可
* root的左子樹為:遞迴原本root的右子
* root的右子樹為:遞迴原本root的左子

## Python:

# Definition for a binary tree node.
# class TreeNode(object):
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution(object):
    def invertTree(self, root):
        """
        :type root: TreeNode
        :rtype: TreeNode
        """
        if not root:
            return None
        newLeft=self.invertTree(root.right)
        newRight=self.invertTree(root.left)
        root.left=newLeft
        root.right=newRight
        return root

## C++:

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode() : val(0), left(nullptr), right(nullptr) {}
 *     TreeNode(int x) : val(x), left(nullptr), right(nullptr) {}
 *     TreeNode(int x, TreeNode *left, TreeNode *right) : val(x), left(left), right(right) {}
 * };
 */
class Solution {
public:
    TreeNode* invertTree(TreeNode* root) {
        if (root==nullptr) return nullptr;
        TreeNode* newLeft= invertTree(root->right);
        TreeNode* newRight= invertTree(root->left);
        root->left= newLeft;
        root->right= newRight;
        return root;
    }
};