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() - ; ; ){
             if(str[i] == '#'){
                 str = str.substr(, i - );
                 i = str.length() - ;
             }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 = ; 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 + ;  //跳过','符号
             }
         }
         sz = dataVec.size();
         TreeNode * root = new TreeNode(atoi(dataVec[].c_str()));
         queue<TreeNode *>q;
         q.push(root);
         int  i = ;
         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。