leetcode

0 class Solution {

1 public:

2 TreeNode *invertTree(TreeNode *root) {

3 if (!root) return nullptr;

4

5 stack<TreeNode *> st;

6 st.push(root);

7 while (!st.empty()) {

8 TreeNode *root = st.top();

9 st.pop();

10 swap(root->left, root->right);

11 if (root->left) st.push(root->left);

12 if (root->right) st.push(root->right);

13 }

14 return root;

15 }

16 };