解析

//! log(n)~n,n
class Solution {
 public:
  TreeNode *invertTree(TreeNode *root) {
    dfsModify(root);
    return root;
  }
  void dfsModify(TreeNode *node) {
    if (node == nullptr) {
      return;
    }
    dfsModify(node->left);
    dfsModify(node->right);

    TreeNode *temp = node->left;
    node->left = node->right;
    node->right = temp;
    return;
  }
};