Thread: Program flow

I rewrote the code but im having trouble defining the InputIterator1 first1, InputIterator1 last1 members when using strings with set_intersection.

Code:

void read_file(const char*, set<string>& );
 
int main ()
{
   set<string> sWords1;
   set<string> sWords2;
  
   read_file("1.txt", sWords1);
   read_file("2.txt", sWords2);
  
   vector<string> v;
   vector<string>::iterator it;
  
   it = set_intersection (sWords1, sWords1.size(), sWords2, sWords2.size(), v.begin());   // having trouble here
  
   cout << "Intersection has " << int(it - v.begin()) << " elements.\n";
  
   for (size_t i = 0; i != v.size(); ++i)
          cout << "The "<< i+1 <<"." << " element is: " << v[i] << "\n";
  
  system("pause");
  return 0;
}
  
  void read_file(const char* name, vector<string>& vWords)
  {
    ifstream file(name);
    string line;
    vWords.clear();
    while (getline(file, line, ' ')) {
        vWords.push_back(line);
    }
  }

You don't have space in your vector for the intersection. Use a std::back_inserter(v) instead of v.begin(). Then you can just use v.size() to get the number of elements.

Use sWords1.begin(), sWords1.end(), sWords2.begin(), sWords2.end() as the other arguments.


Also, read_file takes a vector, but you're trying to pass a set. That won't work. Either make sWords1/2 vectors (but then you need to sort them afterwards), or make read_file take a set and change the insertion function accordingly.

Thank you very much!

I chose to make sWords1/2 vectors because the set container doesnt have a push_back function.
I sorted vWords1/2 out but i still get an error.

Code:

int main ()
{
  vector<string> vWords1;
  vector<string> vWords2;
  
  read_file("1.txt", vWords1);
  read_file("2.txt", vWords2);

  sort (vWords1.begin(), vWords1.end()); 
  sort (vWords2.begin(), vWords2.end());  
  
  vector<string> v;
  vector<string>::iterator it;
  
  it = set_intersection (vWords1.begin(), vWords1.end(), vWords2.begin(), vWords2.end(), back_inserter(v));
  // error here
  cout << "Intersection has " << v.size() << " elements.\n";
  for (size_t i = 0; i != v.size(); ++i)
    cout << "The "<< i+1 <<"." << " element is: " << v[i] << "\n";
  
  system("pause");
  return 0;
}
  void read_file(const char* name, vector<string>& vWords)
  {
    ifstream file(name);
    string line;
    vWords.clear();
    while (getline(file, line)) {
        vWords.push_back(line);
    }
   }

what error?

no match for 'operator=' in 'it = std::set_intersection [with_InputIterator1=__gnu_cxx::__normal_iterator<s td::string* ... etc.

btw i included #include <iterator>

Oh yeah. Don't assign the return value to anything. It's useless in this case. You just get back the back_insert_iterator you passed in. Just use the vector as it is. If you need a pair of iterators for the intersection, use v.begin() and v.end().