58、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

/*
struct TreeNode {
    int val;
    struct TreeNode *left;
    struct TreeNode *right;
    TreeNode(int x) :
            val(x), left(NULL), right(NULL) {
    }
};
*/


typedef TreeNode* pnode;

class Solution {  
public:
    char* Serialize(TreeNode *root) {
       if(root == NULL)
           return NULL;
        
        string str;
        Serialize(root, str);
        
        char *ret = new char[str.length() + 1];
        
        int i;
        
        for(i = 0; i < str.length(); i++){
            ret[i] = str[i];
        }
        
        ret[i] = '\0';
        return ret;
    }
    
    void Serialize(TreeNode *root, string& str){
        if(root == NULL){
            str += '#';
            return ;
        }
        
        string r = to_string(root->val);
        str += r;
        str += ',';
        
        Serialize(root->left, str);
        
        Serialize(root->right, str);
        
    }
     
    TreeNode* Deserialize(char *str) {
        if(str == NULL)
            return NULL;
        
        TreeNode *ret = Deserialize(&str);
 
        return ret;
    }
    
    TreeNode* Deserialize(char **str){//由于递归时，会不断的向后读取字符串
        if(**str == '#'){  //所以一定要用**str,
            ++(*str);         //以保证得到递归后指针str指向未被读取的字符
            return NULL;
        }
        
        int num = 0;
        
        while(**str != '\0' && **str != ','){
            num = num*10 + ((**str) - '0');
            ++(*str);
        }
        
        TreeNode *root = new TreeNode(num);
        if(**str == '\0')
            return root;
        else
            (*str)++;
        
        root->left = Deserialize(str);
        root->right = Deserialize(str);
        
        return root;
    }
};