LeetCode OJ：Serialize and Deserialize Binary Tree（对树序列化以及解序列化）

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.

For example, you may serialize the following tree

    1
   / 
  2   3
     / 
    4   5

as "[1,2,3,null,null,4,5]", just the same as how LeetCode OJ serializes a binary tree. You do not necessarily need to follow this format, so please be creative and come up with different approaches yourself.

这题实际上思路还是比较清晰的，遇见NULL的话那么存入一个#既可以了，解序列化的时候直接相应的处理#就可以了，代码如下：

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Codec {
public:

    // Encodes a tree to a single string.
    string serialize(TreeNode* root) {
        queue<TreeNode *> q;
        string str = "";
        if(!root) return str;
        stringstream ss;
        ss << root->val;
        str += ss.str();
        q.push(root);
        while(!q.empty()){
            TreeNode * t = q.front();
            if(t->left) q.push(t->left);
            if(t->right) q.push(t->right);
            if(t->left){
                ss.str("");
                ss << "," << t->left->val;
                str += ss.str();
            }else{
                ss.str("");
                ss << "," << "#";
                str += ss.str(); 
            }

            if(t->right){
                ss.str("");
                ss << "," << t->right->val;
                str += ss.str();
            }else{
                ss.str("");
                ss << "," << "#";
                str += ss.str();
            }
            q.pop();
        }
        //删除末尾的#字符
        for(int i = str.length() - 1; ; ){
            if(str[i] == '#'){
                str = str.substr(0, i - 1);
                i = str.length() - 1;
            }else{
                break;
            }
        }
        return str;
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        if(!data.size()) return NULL;
        vector<string> dataVec;
        int sz = data.length();
        for(int i = 0; i < sz;){//分割字符串，保存到vector中
            if(data[i] != ','){
                int j = i;
                for(; j < sz && data[j] != ','; ++j)
                    ;
                string tmp = data.substr(i, j - i);//注意substr的使用细节
                dataVec.push_back(tmp);
                i = j + 1;  //跳过','符号
            }
        }
        sz = dataVec.size();
        TreeNode * root = new TreeNode(atoi(dataVec[0].c_str()));
        queue<TreeNode *>q;
        q.push(root);
        int  i = 1;
        while(!q.empty() && i < sz){
            TreeNode * t = q.front();
            if(dataVec[i] != "#"){
                t->left = new TreeNode(atoi(dataVec[i].c_str()));
                q.push(t->left);
            }else{
                t->left = NULL;
            }
            i++;
            if(i >= sz) break;
            if(dataVec[i] != "#"){
                t->right = new TreeNode(atoi(dataVec[i].c_str()));
                q.push(t->right);
            }else{
                t->right = NULL;
            }
            q.pop();
            i++;
        }
        return root;
    }
};

吐槽一下，c++连个split函数都没有，写起来真是恶心，还要自己去分割字符串。