# LeetCode.606.Construct String from Binary Tree 二叉树转括号字符串

## 题目描述

606 Construct String from Binary Tree
https://leetcode-cn.com/problems/construct-string-from-binary-tree/

You need to construct a string consists of parenthesis and integers from a binary tree with the preorder traversing way.

The null node needs to be represented by empty parenthesis pair “()”. And you need to omit all the empty parenthesis pairs that don’t affect the one-to-one mapping relationship between the string and the original binary tree.

Example 1:

Input: Binary tree: [1,2,3,4]
1
/   \
2     3
/
4

Output: "1(2(4))(3)"

Explanation: Originallay 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: Binary tree: [1,2,3,null,4]
1
/   \
2     3
\
4

Output: "1(2()(4))(3)"

Explanation: Almost the same as the first example,
except we can't omit the first parenthesis pair to break the one-to-one mapping relationship between the input and the output.

## 解题过程

public String tree2str(TreeNode t) {
if (null == t) {
return "";
}
if (null == t.left && null == t.right) {
return String.valueOf(t.val);
}
StringBuilder sb = new StringBuilder(String.valueOf(t.val));
sb.append("(").append(tree2str(t.left)).append(")");
if (null != t.right) {
sb.append("(").append(tree2str(t.right)).append(")");
}
return sb.toString();
}

## GitHub代码

algorithms/leetcode/leetcode/_606_ConstructStringFromBinaryTree.java
https://github.com/masikkk/algorithms/blob/master/leetcode/leetcode/_606_ConstructStringFromBinaryTree.java

342

#### 页面信息

location:
protocol:
host:
hostname:
origin:
pathname:
href:
document:
referrer:
navigator:
platform:
userAgent: