How to make elements of vector unique? (remove non adjacent duplicates)

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I think you would do it like this:

I would use two iterators on the vector :

The first of one reads the data and inserts it a temporary set.

When the read data was not in the set you copy it from the first iterator to the second and increment it.

At the end you keep only the data up to the second iterator.

The complexity is O( n .log( n ) ) as the lookup for duplicated elements uses the set, not the vector.

#include <vector>
#include <set>
#include <iostream>

int main(int argc, char* argv[])
{
    std::vector< int > k ;

    k.push_back( 2 );
    k.push_back( 1 );
    k.push_back( 6 );
    k.push_back( 1 );
    k.push_back( 4 );
    k.push_back( 6 );
    k.push_back( 2 );
    k.push_back( 1 );
    k.push_back( 1 );

{
    std::vector< int >::iterator r , w ;

    std::set< int > tmpset ;

    for( r = k.begin() , w = k.begin() ; r != k.end() ; ++r )
    {
        if( tmpset.insert( *r ).second )
        {
            *w++ = *r ;
        }
    }

    k.erase( w , k.end() );
}


    {
        std::vector< int >::iterator r ;

        for( r = k.begin() ; r != k.end() ; ++r )
        {
            std::cout << *r << std::endl ;
        }
    }
}

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