449

/**
 * Definition for a binary tree node.
 * struct TreeNode {
 *     int val;
 *     TreeNode *left;
 *     TreeNode *right;
 *     TreeNode(int x) : val(x), left(NULL), right(NULL) {}
 * };
 */
class Codec {
public:

    // Encodes a tree to a single string.
    string serialize(TreeNode* root) {
        if(!root) return "#";
        return to_string(root->val)+","+serialize(root->left)+","+serialize(root->right);
    }

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

    TreeNode* dserialize(string &data, int &idx){
        if(data[idx] == '#'){
            if(data.length()-idx > 1)
                idx += 2;
            return NULL;
        }
        int val = 0;
        while(idx < data.length() && isdigit(data[idx])){
            val = val*10+data[idx]-'0';
            idx++;
        }
        if(idx<data.length()-1) idx++;
        TreeNode* node = new TreeNode(val);
        node->left = dserialize(data, idx);
        node->right = dserialize(data, idx);
        return node;
    }

};

// Your Codec object will be instantiated and called as such:
// Codec* ser = new Codec();
// Codec* deser = new Codec();
// string tree = ser->serialize(root);
// TreeNode* ans = deser->deserialize(tree);
// return ans;