297. Serialize and Deserialize Binary Tree #

Problem #

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

Problem Summary #

Design an algorithm to serialize and deserialize a binary tree. There is no restriction on how to serialize and deserialize it, but you need to ensure that the binary tree can be serialized into a string, and that this string can be deserialized into the original binary tree.

Solution Approach #

• 1. Imagine the given binary tree as a full binary tree (nonexistent nodes are filled with null).
• 2. Through preorder traversal, you can obtain a sequence whose first node is the root, and then recursively serialize/deserialize it.

Code #

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(),
	}
}