Wykrywanie duplikatów

#include <iostream>
#include <vector>
#include <algorithm>
#include <iterator>

// Kompilować w trybie C++11

using namespace std;

template < class T >
T intersection_without_sort( const T & cont1, const T & cont2 ) {
    auto inter = T();
    auto cit = cont1.cbegin();
   
    while( cit != cont1.cend() ) {
        cit = find_first_of( cit, cont1.cend(), cont2.cbegin(), cont2.cend() );
        if( inter.cend() == find( inter.cbegin(), inter.cend(), * cit ) ) {
            inter.push_back( * cit );
        }
        ++cit;
    }
   
    return inter;
}

int main() {
    auto vec1 = vector < int > { 1, 3, 2, 1, 2 };
    auto vec2 = vector < int > { 2, 4, 3, 32, 1, 1 };
   
    auto answer = intersection_without_sort( vec1, vec2 );
   
    copy( answer.cbegin(), answer.cend(), ostream_iterator < int >( cout, " " ) );
    cout << endl;
}