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) {
    }
};
*/
class Solution {
public:
    /*=========================二叉树序列化==============================*/
	char* Serialize(TreeNode *root) {
		if (root == NULL)
			return NULL;
		string str;
		serialize(root, str);
		char* buffer = new char[str.size() + 1];
		strcpy(buffer, str.c_str());                     //将string类型的字符串转换成C_style类型并复制到一个char类型数组  
		return buffer;
	}

	void serialize(TreeNode* root, string& str)
	{
		if (root == NULL)
		{
			str += "$,";                      //叶子结点的左右子结点为空则用 $ 来代替  
			return;
		}
		str += to_string(root->val);             //将结点值（int）转换成字符串（string）类型  
		str += ',';
		serialize(root->left, str);             //递归序列化结点的左子树  
		serialize(root->right, str);            //递归序列化结点的右子树  
	}

	/*========================二叉树反序列化============================*/
	TreeNode* Deserialize(char *str) {
		if (str == NULL)
			return NULL;
		return deserialize(&str);
	}

	TreeNode* deserialize(char** str)
	{
		if (**str == '$')
		{
			(*str) += 2;
			return NULL;
		}
		int val = 0;
		while (**str != ','&&**str != '\0')                //把字符串类型的数字转换成int类型的数字  
		{
			val = val * 10 + (**str - '0');
			++(*str);
		}
		TreeNode* root = new TreeNode(val);               //构建根结点  
		if (**str == '\0')
			return root;
		else
			++(*str);
		root->left = deserialize(str);                    //递归的构建左子树结点  
		root->right = deserialize(str);                   //递归的构建右子树结点  
		return root;
	}
};