剑指offer：序列化二叉树

题目描述

请实现两个函数，分别用来序列化和反序列化二叉树

思路

序列化就是把一棵树按照某种序列，转化成字符串，反序列化反之。
1
2 3
4 5 6
先序序列化是 1,2,4,#,#,#,3,5,#,#,6,#,#
递归实现

code

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};
*/
class Solution {
public:
    void  serialize(TreeNode *root,string &s){
        if(root==nullptr){
            s=s+'#'+',';
            return;
        }
        s=s+to_string(root->val)+",";
        serialize(root->left,s);
        serialize(root->right,s);
    }
    char* Serialize(TreeNode *root) {    
        string res="";
        if(root==nullptr)
            return nullptr;
        serialize(root,res);
        char *ret = new char[res.length() + 1];
        strcpy(ret, res.c_str());
        return ret;
    }
    TreeNode *deserializeHelper(string &s)
    {
        if (s.empty())
            return nullptr;
        if (s[0] == '#')
        {
            s = s.substr(2);
            return nullptr;
        }
        TreeNode *ret = new TreeNode(stoi(s));
        s = s.substr(s.find_first_of(',') + 1);
        ret->left = deserializeHelper(s);
        ret->right = deserializeHelper(s);
        return ret;
    }
    TreeNode* Deserialize(char *str) {
        if(str==nullptr)
            return nullptr;
        string s=str;
        return deserializeHelper(s);
    }
};