0297. Serialize and Deserialize Binary Tree

# 297. Serialize and Deserialize Binary Tree#

## 题目 #

Serialization is the process of converting a data structure or object into a sequence of bits so that it can be stored in a file or memory buffer, or transmitted across a network connection link to be reconstructed later in the same or another computer environment.

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how your serialization/deserialization algorithm should work. You just need to ensure that a binary tree can be serialized to a string and this string can be deserialized to the original tree structure.

Clarification: The input/output format is the same as  how LeetCode serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

Example 1:

``````Input: root = [1,2,3,null,null,4,5]
Output: [1,2,3,null,null,4,5]
``````

Example 2:

``````Input: root = []
Output: []
``````

Example 3:

``````Input: root = [1]
Output: [1]
``````

Example 4:

``````Input: root = [1,2]
Output: [1,2]
``````

Constraints:

• The number of nodes in the tree is in the range `[0, 104]`.
• `1000 <= Node.val <= 1000`

## 解题思路 #

1. 将给定的二叉树想象成一颗满二叉树(不存在的结点用 null 填充)。
1. 通过前序遍历，可以得到一个第一个结点为根的序列，然后递归进行序列化/反序列化即可。

## 代码 #

``````package leetcode

import (
"strconv"
"strings"

"github.com/halfrost/leetcode-go/structures"
)

type TreeNode = structures.TreeNode

type Codec struct {
builder strings.Builder
input   []string
}

func Constructor() Codec {
return Codec{}
}

// Serializes a tree to a single string.
func (this *Codec) serialize(root *TreeNode) string {
if root == nil {
this.builder.WriteString("#,")
return ""
}
this.builder.WriteString(strconv.Itoa(root.Val) + ",")
this.serialize(root.Left)
this.serialize(root.Right)
return this.builder.String()
}

// Deserializes your encoded data to tree.
func (this *Codec) deserialize(data string) *TreeNode {
if len(data) == 0 {
return nil
}
this.input = strings.Split(data, ",")
return this.deserializeHelper()
}

func (this *Codec) deserializeHelper() *TreeNode {
if this.input[0] == "#" {
this.input = this.input[1:]
return nil
}
val, _ := strconv.Atoi(this.input[0])
this.input = this.input[1:]
return &TreeNode{
Val:   val,
Left:  this.deserializeHelper(),
Right: this.deserializeHelper(),
}
}
``````

Apr 8, 2023