leetcode

0 class Solution {

1 public:

2 string tree2str(const TreeNode *root) {

3 stack<const TreeNode *> stack;

4 stack.push(root);

5 string res = "";

6

7 while (!stack.empty()) {

8 const TreeNode *temp = stack.top();

9 stack.pop();

10 if (temp == nullptr)

11 res += ')';

12 else {

13 res += '(' + to_string(temp->val);

14 stack.push(nullptr);

15

16 if (temp->right) stack.push(temp->right);

17

18 if (temp->left)

19 stack.push(temp->left);

20 else if (temp->right)

21 res += "()";

22 }

23 }

24 return res.substr(1, res.size() - 2);

25 }

26 };