vectors and find

how does the find STL function work with strings? The code below doesn't work correctly. The purpose is to build a list of unique words. If the word is not in the vector, then add it.

Code:

---


void foo()
{
    fstream stream;
    vector<string> theList;
    string oneWord;
    stream.open(...);  // open the file for reading

    while( !stream.eof())
    {
        stream >> oneWord;
        vector<string>::iterator pos;
        pos = find( theList.begin(), theList.end(), oneWord);
        if(pos == NULL)
              theList.push_back(oneWord);
      }
}

---

First, find returns an iterator representing the item or end() if it is not found. So you need to check for pos == theList.end() instead of NULL.

Second, this is probably not the best choice of containers for doing this operation. A better choice might be to use std::set (this might not be the best choice, but it will certainly be better than using a vector).

Best regards,
John

std::set would definitely be the way to go. Elements are automatically sorted and duplicates are not permitted.

Thanks for both your replies. Here are the changes that works. Any other suggestions for improvement?

Code:

---

set<string> theArray;
void foo(string& str)
{
        string oneWord;
        fstream stream;
        stream.open(str.c_str(), ios::in);
        while(!stream.eof())
        {
            stream >> oneWord;
            set<string>::iterator pos;
            pos = theArray.find(oneWord);
            if(pos == theArray.end() )
            {
                  theArray.insert(oneWord);
            }
        }
        stream.close();
}

---

Yes, don't bother checking if the item is in the set before the insert. The set will take care of that for you. So, just do the following:

Code:

---

set<string> theArray;
void foo(string& str)
{
        string oneWord;
        fstream stream;
        stream.open(str.c_str(), ios::in);
        while(!stream.eof())
        {
            stream >> oneWord;
                    theArray.insert(oneWord);
        }
        stream.close();
}

---

Best regards,
John