> For the complete documentation index, see [llms.txt](https://garylai.gitbook.io/algorithm-and-data-structure/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://garylai.gitbook.io/algorithm-and-data-structure/problems/tree/serialization-and-deserialization/construct-string-from-binary-tree.md).

# 606. Construct String from Binary Tree

[606. Construct String from Binary Tree](https://leetcode.com/problems/construct-string-from-binary-tree/)

```python
# Definition for a binary tree node.
# class TreeNode:
#     def __init__(self, val=0, left=None, right=None):
#         self.val = val
#         self.left = left
#         self.right = right
class Solution:
    def tree2str(self, root: Optional[TreeNode]) -> str:

        def traverse(root):
            if not root:
                return ''
            left = traverse(root.left)
            right = traverse(root.right)
            if len(left) == 0 and len(right) == 0:
                return str(root.val)
            elif len(left) == 0:
                return str(root.val) + '()' + '(' + right  +')'
            elif len(right) == 0:
                return str(root.val) + '(' + left  +')'
            return str(root.val) + '(' + left + ')' + '(' + right  +')'
        return traverse(root)
```