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#include <algorithm>
#include <iterator>
#include <iostream>
#include <vector>
//
// Remove unique elements to the end of the sorted range. Returns an iterator
// to the new end of the range.
template <typename ForwardIterator>
ForwardIterator
anti_unique( ForwardIterator begin, ForwardIterator end )
{
ForwardIterator result = begin;
ForwardIterator first_equal = begin;
size_t count_equal = 1;
while (++begin != end)
{
if (*begin == *first_equal) ++count_equal;
else
{
if (count_equal > 1)
{
result = std::copy( first_equal, begin, result );
}
first_equal = begin;
count_equal = 1;
}
}
if (count_equal > 1)
{
result = std::copy( first_equal, begin, result );
}
return result;
}
//
int main()
{
using namespace std;
int _xs[] = { 6, 1, 3, 4, 1, 7, 5, 3, 7 };
vector <int> xs( _xs, _xs + (sizeof( _xs ) / sizeof( int )) );
vector <int> ys( xs ); // copy
sort( ys.begin(), ys.end() ); // sort
ys.erase( anti_unique( ys.begin(), ys.end() ), ys.end() );
cout << "nonunique elements: ";
copy( ys.begin(), ys.end(), ostream_iterator <int> ( cout, " " ) );
cout << endl;
return 0;
}
 