leetcode

0 class Solution {

1 public:

2 int kthSmallest(TreeNode *root, int k) {

3 stack<TreeNode *> st;

4 while (true) {

5 while (root) {

6 st.push(root);

7 root = root->left;

8 }

9 if (st.empty()) break;

10 root = st.top(), st.pop();

11 if (!--k) return root->val;

12 root = root->right;

13 }

14 return -1;

15 }

16 };