class Solution {
public:
void traversal(TreeNode* root){
if (!root) return;
std::swap(root->left, root->right);
// TreeNode* tmp = root->right;
// root->right = root->left;
// root->left = tmp;
traversal(root->left);
traversal(root->right);
}
TreeNode* invertTree(TreeNode* root) {
traversal(root);
return root;
}
};