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;
- include <set>
- include <algorithm>
- 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>
- include <set>
- 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>