public class Solution
extends Object
606 - Construct String from Binary Tree\.
Easy
Given the `root` of a binary tree, construct a string consisting of parenthesis and integers from a binary tree with the preorder traversal way, and return it.
Omit all the empty parenthesis pairs that do not affect the one-to-one mapping relationship between the string and the original binary tree.
**Example 1:**
**Input:** root = [1,2,3,4]
**Output:** "1(2(4))(3)"
**Explanation:** Originally, it needs to be "1(2(4)())(3()())", but you need to omit all the unnecessary empty parenthesis pairs. And it will be "1(2(4))(3)"
**Example 2:**
**Input:** root = [1,2,3,null,4]
**Output:** "1(2()(4))(3)"
**Explanation:** Almost the same as the first example, except we cannot omit the first parenthesis pair to break the one-to-one mapping relationship between the input and the output.
**Constraints:**
* The number of nodes in the tree is in the range [1, 104].
* `-1000 <= Node.val <= 1000`