Remove duplicate elements from std::vector but starting from the front?

How can I delete duplicate elements from a vector but starting from the front?

So

2 3 4 5 2 5 would become 3 4 2 5

1 5 3 1 would become 5 3 1

I would like the solution to be easy to read, and it would be nice if it had good performance as well.

If a container supports bidirectional iterators then it is unimportant from which side of the container you are trying to remove duplicate elements because you can use reverse iterators.

Here is a demonstrative program.

#include <iostream> 
#include <vector> 
#include <iterator> 
#include <algorithm> 
  
template <typename ForwardIterator> 
ForwardIterator remove_duplicates( ForwardIterator first, ForwardIterator last ) 
{ 
    for ( ; first != last; ++first ) 
    { 
        last = std::remove( std::next( first ), last, *first ); 
    } 
      
    return last; 
} 
  
int main() 
{ 
    std::vector<int> v = { 1, 2, 3, 4, 5, 4, 3, 2, 1 }; 
      
    for ( const auto &item : v ) std::cout << item << ' '; 
    std::cout << '\n'; 
  
    v.erase( remove_duplicates( std::begin( v ), std::end( v ) ), std::end( v ) ); 
      
    for ( const auto &item : v ) std::cout << item << ' '; 
    std::cout << '\n'; 
  
    std::cout << '\n'; 
      
    v.assign( { 1, 2, 3, 4, 5, 4, 3, 2, 1 } ); 
  
    for ( const auto &item : v ) std::cout << item << ' '; 
    std::cout << '\n'; 
      
    v.erase( std::begin( v ), remove_duplicates( std::rbegin( v ), std::rend( v ) ).base() ); 
     
    for ( const auto &item : v ) std::cout << item << ' '; 
    std::cout << '\n'; 
} 

The program output is

1 2 3 4 5 4 3 2 1 
1 2 3 4 5 

1 2 3 4 5 4 3 2 1 
5 4 3 2 1