LeetCode 297. 二叉树的序列化与反序列化

class Codec {
public:
    string path;
    // Encodes a tree to a single string.
    string serialize(TreeNode* root) {
        dfs_s(root);
        return path;
    }

    void dfs_s(TreeNode* root){
        if(!root) path+="#,";
        else{
            path+=to_string(root->val)+',';
            dfs_s(root->left);
            dfs_s(root->right);
        }
    }

    // Decodes your encoded data to tree.
    TreeNode* deserialize(string data) {
        int u=0;
        return dfs_d(data,u);
    }

    TreeNode* dfs_d(string& data,int& u){
        if(data[u]=='#'){
            u+=2;
            return NULL;
        }else{
            int k=u;
            while(data[u]!=',') u++;
            auto root = new TreeNode(stoi(data.substr(k,u-k)));
            u++;
            root->left = dfs_d(data,u);
            root->right = dfs_d(data,u);
            return root;
        }
    }
};

// Your Codec object will be instantiated and called as such:
// Codec ser, deser;
// TreeNode* ans = deser.deserialize(ser.serialize(root));