LeetCode #297 - Serialize and Deserialize Binary Tree

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本文介绍了一种二叉树的序列化及反序列化方法，使用前序遍历并以特定符号标记空节点。通过递归方式实现了序列化字符串与二叉树结构之间的转换。

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题目描述：

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.

Example:

You may serialize the following tree:

    1
   / \
  2   3
     / \
    4   5

as "[1,2,3,null,null,4,5]"

Clarification: The above 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.

Note: Do not use class member/global/static variables to store states. Your serialize and deserialize algorithms should be stateless.

自行定义一种将二叉树序列化，并且去序列化的方法。选取前序遍历的顺序作为二叉树序列化的方法，遍历到空节点返回‘#’，那么这道题的关键在于必须能够根据序列化后的二叉树，重建恢复成原始的二叉树，实现这一目标需要进行递归。

class Codec {
public:

    // Encodes a tree to a single string.
    string serialize(TreeNode* root) {
        if(root==NULL) return "#/";
        string left=serialize(root->left);
        string right=serialize(root->right);
        string result=to_string(root->val)+"/"+left+right;
        return result;
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        istringstream iss(data);
        return helper(iss);
    }
    
    TreeNode* helper(istringstream& iss)
    {
        string temp;
        getline(iss,temp,'/');
        if(temp=="#") return NULL;
        TreeNode* root=new TreeNode(atoi(temp.c_str()));
        root->left=helper(iss);
        root->right=helper(iss);
        return root;
    }
};