/**

* 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) {

// 종료 조건

if (!root)

return (nullptr);

// 노드 반전 (중위순회)

TreeNode* tmp = root->left;

root->left = root->right;

root->right = tmp;

// 재귀적 호출

invertTree(root->left);

invertTree(root->right);

return (root);

}

};