leetcode

0 class Solution {

1 public:

2 bool isBalanced(TreeNode *root) {

3 if (!root) return true;

4 stack<TreeNode *> st;

5 st.push(root);

6 while (!st.empty()) {

7 TreeNode *root = st.top();

8 if (root == nullptr) {

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

10 int left = root->left ? root->left->val : 0;

11 int right = root->right ? root->right->val : 0;

12 if (abs(right - left) > 1) return false;

13 root->val = max(left, right) + 1;

14 continue;

15 }

16 st.push(nullptr);

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

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

19 }

20 return true;

21 }

22 };