I've tried to implement hash table using vector. My table size will be defined in the constructor, for example lets say table size is 31, to create hash table I do followings:

```
vector<string> entires; // it is filled with entries that I'll put into hash table; 
vector<string> hashtable;
hashtable.resize(31);
for(int i=0;i<entries.size();i++){
    int index=hashFunction(entries[i]);
    // now I need to know whether I've already put an entry into hashtable[index] or not 
}

```

Is there anyone to help me how could I do that ?