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2010-05-25T14:21:17Z

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2010-05-25T10:29:42Z

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==Add elements into an integer set and output all added elements==

<source lang="cpp">/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <set>
#include <algorithm>
#include <iterator>
using namespace std;
int main()
{
/* type of the collection:
* - duplicates allowed
* - elements are integral values
* - descending order
*/
typedef multiset<int,greater<int> > IntSet;
IntSet coll1; // empty multiset container
// insert elements in random order
coll1.insert(4);
coll1.insert(3);
coll1.insert(5);
coll1.insert(1);
coll1.insert(6);
coll1.insert(2);
coll1.insert(5);
// iterate over all elements and print them
IntSet::iterator pos;
for (pos = coll1.begin(); pos != coll1.end(); ++pos) {
cout << *pos << " ";
}
cout << endl;
}</source>
<pre class=codeResult>6 5 5 4 3 2 1</pre>

==Assign elements to another multiset with ascending order==

<source lang="cpp">/* The following code example is taken from the book
* "The C++ Standard Library - A Tutorial and Reference"
* by Nicolai M. Josuttis, Addison-Wesley, 1999
*
* (C) Copyright Nicolai M. Josuttis 1999.
* Permission to copy, use, modify, sell and distribute this software
* is granted provided this copyright notice appears in all copies.
* This software is provided "as is" without express or implied
* warranty, and with no claim as to its suitability for any purpose.
*/
#include <iostream>
#include <set>
#include <algorithm>
#include <iterator>
using namespace std;
int main()
{
/* type of the collection:
* - duplicates allowed
* - elements are integral values
* - descending order
*/
typedef multiset<int,greater<int> > IntSet;
IntSet coll1; // empty multiset container
// insert elements in random order
coll1.insert(4);
coll1.insert(3);
coll1.insert(5);
coll1.insert(1);
coll1.insert(6);
coll1.insert(2);
coll1.insert(5);
// iterate over all elements and print them
IntSet::iterator pos;
for (pos = coll1.begin(); pos != coll1.end(); ++pos) {
cout << *pos << " ";
}
cout << endl;
// assign elements to another multiset with ascending order
multiset<int> coll2(coll1.begin(),
coll1.end());

// print all elements of the copy
copy (coll2.begin(), coll2.end(),
ostream_iterator<int>(cout," "));
cout << endl;
}</source>
<pre class=codeResult>6 5 5 4 3 2 1
1 2 3 4 5 5 6</pre>

==Define multiset< int, less< int > >==

<source lang="cpp">#include <iostream>
#include <set>
#include <algorithm>
using namespace std;
int main()
{
const int SIZE = 10;
int a[ SIZE ] = { 7, 22, 9, 1, 18, 30, 100, 22, 85, 13 };
typedef multiset< int, less< int > > ims;
ims intMultiset; // ims for "integer multiset"
cout << "There are currently " << intMultiset.count( 15 )
<< " values of 15 in the multiset\n";
return 0;
}</source>

==Initializing Associative Containers==

<source lang="cpp">#include <algorithm>
#include <functional>
#include <iostream>
#include <map>
#include <set>
#include <utility>
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_cars = 6;
const int year[num_cars] = { 1998, 1970, 1966, 2004, 1998, 1930 };
const char* name[num_cars] = { "A", "B","C", "D", "E","F" };
set<int> unique_years( year, year + num_cars );
multiset<int> all_years( year, year + num_cars );
print( unique_years );
print( all_years );
typedef map<string,int> Car_map;
Car_map unique_cars;
transform( name, name+num_cars, year,inserter( unique_cars, unique_cars.end() ),make_pair<string,int> );
Car_map::const_iterator unique_cars_end = unique_cars.end();
for( Car_map::const_iterator i = unique_cars.begin();i != unique_cars_end; ++i )
cout << i->second << " " << i->first << endl;
typedef multimap<string,int> Car_multimap;
Car_multimap all_cars;
transform( name, name+num_cars, year,inserter( all_cars, all_cars.end() ),make_pair<string,int> );
Car_multimap::const_iterator all_cars_end = all_cars.end();
for( Car_multimap::const_iterator i = all_cars.begin();i != all_cars_end; ++i )
cout << i->second << " " << i->first << endl;
}</source>

==Modify or Remove a Value in a Set or Multiset==

<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;
multiset<int>::size_type num_wrong = all.erase( wrong_grade );
if( num_wrong > 0 ) {
vector<int> right( num_wrong, right_grade );
all.insert( right.begin(), right.end() );
unique.erase( wrong_grade );
unique.insert( right_grade );
}
else
cout << "No wrong grades of " << wrong_grade << endl;
const int drop_grade = 5;
multiset<int>::iterator spot = all.find( drop_grade );
if( spot != all.end() ) {
all.erase( spot );
if( all.count( drop_grade ) == 0 )
unique.erase( drop_grade );
}
else
cout << "Couldn"t find a grade of " << drop_grade << endl;
print( unique);
print( all);
}</source>

==Use std::copy to print all elements in a multiset==

<source lang="cpp">#include <iostream>
using std::cout;
using std::endl;
#include <set> // multiset class-template definition
#include <algorithm> // copy algorithm
#include <iterator> // ostream_iterator
int main()
{
int a[ 10 ] = { 7, 22, 9, 1, 18, 30, 100, 22, 85, 13 };
std::multiset< int, std::less< int > > intMultiset;
std::ostream_iterator< int > output( cout, " " );
// insert elements of array a into intMultiset
intMultiset.insert( a, a + 10 );
cout << "\nAfter insert, intMultiset contains:\n";
std::copy( intMultiset.begin(), intMultiset.end(), output );

cout << endl;
return 0;
}</source>
<pre class=codeResult>After insert, intMultiset contains:
1 7 9 13 18 22 22 30 85 100</pre>

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