序列化二叉树

class Solution {
public:
char* Serialize(TreeNode *root) {
if (!root)
return nullptr;
string resStr; //存放结果
serializeTree(root, resStr);

    char *res = new char[resStr.length() +1];
    strcpy(res, const_cast<char*>(resStr.c_str()));
    return res;
}
TreeNode* Deserialize(char *str) {
    TreeNode *root = nullptr;
    if (!str)
        return root;
    int length = strlen(str);
    int index = 0;
    DeserializeTree(&root, str, length - 1, index);
    return root;
}

private:
//序列化递归
void serializeTree(TreeNode* root, string &str)
{
if (!root)
{
str = str + "#!";
return;
}
string newChar = to_string(root->val);
str += newChar;
str += '!';
//if (root->left) //错误1：递归里面会有 空节点的处理！！
serializeTree(root->left, str);
//if (root->right)
serializeTree(root->right, str);
}

//反序列化递归建树
void DeserializeTree(TreeNode **pRoot, char*strChar, int length, int &index)
{
    string str; //该节点存放的数值的字符表达
    while (strChar[index] != '!')
    {
        str += strChar[index++];
    }//循环结束 index 指向 ’!'

    if (str == "#") //若为空节点
    {
        index++;
        return;
    }
    else { //若不为空结点
        int val = atoi(str.c_str());
        *pRoot = new TreeNode(val);
        (*pRoot)->val = val;
        index++;
        if (index <= length)
        {
            DeserializeTree(&(*pRoot)->left, strChar, length, index);
        }
        if (index <= length)
        {
            DeserializeTree(&(*pRoot)->right, strChar, length, index);
        }
    }
}

};