leetcode

0 class Solution {

1 public:

2 int sumNumbers(TreeNode *root) {

3 if (!root) return 0;

4

5 int sum = 0, res = 0;

6 stack<pair<TreeNode *, int>> st;

7 while (true) {

8 while (root) {

9 sum *= 10;

10 sum += root->val;

11 if (root->right)

12 st.push({root->right, sum});

13 else if (!root->left)

14 res += sum;

15 root = root->left;

16 }

17 if (st.empty()) break;

18 root = st.top().first;

19 sum = st.top().second;

20 st.pop();

21 }

22

23 return res;

24 }

25 };