vectors and find

[stober]

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.

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);
      }
}

[jwbarton]

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

[Federal102]

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

[stober]

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

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();
}

[jwbarton]

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:

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