C++ Tutorial/set multiset/set insert

set.insert returns pair: p.first represents location and p.second represents the successfulness

<source lang="cpp">#include <iostream> using std::cout; using std::endl;

1. include <set>
2. include <algorithm>
3. include <iterator> // ostream_iterator

int main() {

  double a[ 5 ] = { 2.1, 4.2, 9.5, 2.1, 3.7 };
  std::set< double, std::less< double > > doubleSet( a, a + 5 );;
  std::ostream_iterator< double > output( cout, " " );
  // p represents pair containing const_iterator and bool
  std::pair< std::set< double, std::less< double > >::const_iterator, bool > p;
  p = doubleSet.insert( 13.8 ); // value not in set
  cout << *( p.first ) << ( p.second ? " was" : " was not" ) << " inserted";
  cout << "\ndoubleSet contains: ";
  std::copy( doubleSet.begin(), doubleSet.end(), output );

  cout << endl;
  return 0;

}</source>

13.8 was inserted
doubleSet contains: 2.1 3.7 4.2 9.5 13.8

Use insert() to add element to a set

<source lang="cpp">#include <iostream>

1. include <set>
2. include <vector>

using namespace std; template <class T> void print(T& c){

  for( typename T::iterator i = c.begin(); i != c.end(); i++ ){
     std::cout << *i << endl;
  }

} int main(){

  const int num_grades = 11;
  const int grade[num_grades] = { 2, 5, 3, 8, 9, 9, 6, 3, 5, 9, 10 };
  set<int> unique( grade, grade+num_grades );
  multiset<int> all( grade, grade+num_grades );
  print( unique );
  print( all );
  const int wrong_grade = 9;
  const int right_grade = 10;
  if( unique.erase( wrong_grade ) == 1 ){
     if( unique.insert( right_grade ).second )
        cout << "Added new, unique grade of " << right_grade << endl;
     else
        cout << "Already have unique grade of " << right_grade << endl;
  }
  else
     cout << "No unique grade of " << wrong_grade << endl;
  print( unique);
  print( all);

}</source>