37 序列化与反序列化二叉树

题目

二叉树的序列化是指：把一棵二叉树按照某种遍历方式的结果以某种格式保存为字符串，从而使得内存中建立起来的二叉树可以持久保存。
二叉树的反序列化是指：根据某种遍历顺序得到的序列化字符串结果str，重构二叉树。

C++ 题解

序列化二叉树的过程中，如果遇到空节点，需要以某种符号（这里用#）表示。以下图二叉树为例，序列化二叉树时，需要将空节点也存入字符串中。

// 序列化
void Serialize(const BinaryTreeNode* pRoot, ostream& stream)
{
	if (pRoot == nullptr)
	{
		stream << "#,";
		return;
	}

	stream << pRoot->m_nValue << ',';
	Serialize(pRoot->m_pLeft, stream);
	Serialize(pRoot->m_pRight, stream);
}


bool ReadStream(istream& stream, int* number)
{
	if (stream.eof())
		return false;

	char buffer[32];
	buffer[0] = '\0';

	char ch;
	stream >> ch;
	int i = 0;
	while (!stream.eof() && ch != ',')
	{
		buffer[i++] = ch;
		stream >> ch;
	}

	bool isNumeric = false;
	if (i > 0 && buffer[0] != '#')
	{
		*number = atoi(buffer);
		isNumeric = true;
	}

	return isNumeric;
}

// 反序列化
void Deserialize(BinaryTreeNode** pRoot, istream& stream)
{
	int number;
	if (ReadStream(stream, &number))
	{
		*pRoot = new BinaryTreeNode();
		(*pRoot)->m_nValue = number;
		(*pRoot)->m_pLeft = nullptr;
		(*pRoot)->m_pRight = nullptr;

		Deserialize(&((*pRoot)->m_pLeft), stream);
		Deserialize(&((*pRoot)->m_pRight), stream);
	}
}

python 题解

当遇到当前指向的字符为特殊字符”#”或者指针超出了序列的长度，则返回None，指针后移，继续遍历。

# -*- coding:utf-8 -*-
# class TreeNode:
#     def __init__(self, x):
#         self.val = x
#         self.left = None
#         self.right = None
class Solution:
    flag=-1
    def Serialize(self, root):
        # write code here
        if not root:
            return '#'
        return str(root.val)+','+self.Serialize(root.left)+','+self.Serialize(root.right)

        
    def Deserialize(self, s):
        # write code here
        self.flag+=1
        lis=s.split(',')
        
        if self.flag>=len(s):
            return None
        
        root=None
        if lis[self.flag]!='#':
            root=TreeNode(int(lis[self.flag]))
            root.left=self.Deserialize(s)
            root.right=self.Deserialize(s)
        return root