$ cat ./coding/606-construct-string-from-binary-tree.md

────────────────────────────────────────────────────────────

606. Construct String from Binary Tree

# 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)

$ ls ./coding/ | grep -v 606-construct-string-from-binary-tree