Eliminating repeated values from a vector

Question

Hello, folks briefly my problem is to eliminate repeated values of an array, here is my code and just below a brief explanation.

=========================================================================

#include <iostream>
#include <iterator>

using namespace std;

int* unique( int *first, int *last);
int main(){

int A[] = { 1, 2, 1, 2, 3, 3, 1, 2, 4, 5, 3, 4, 5 };

//aplicar unique sobre A.

auto last = unique(std::begin(A), std::end(A));

//o comando abaixo deveria imprimir A com o conteudo 1, 2, 3, 4, 5.
for( auto i = std::begin(A); i != last; ++i){
    std::cout << *i << " ";
}

std::cout << endl;

//mostrar o novo tamanho de A, que seria 5.
std:: cout << ">>O comprimento logico de A apos o unique() eh: " << std::distance(std::begin(A), last) << std::endl;
std::cout << ">>O retorno indica a posição do elemento: " <<*last << std::endl;


    return 0;
}


int* unique( int *first, int *last){
auto slow = first+2;
    for (auto fast = first+2; fast != last; ++fast){
        for (auto i = slow; i != first; /*empty*/){
            if(*fast != *i ){
                swap(*slow++, *fast);
            }
            --i;
        }
    }
    return slow;
}

=========================================================================

Well, basically I send two pointers indicating the beginning and the end of my vector, then create two more pointers (slow and fast), the fast runs through the vector and tests if the current element is different than the one behind the slow, causing it to push the repeated values to the end of the vector and leaving only the unique values at the beginning, the function returns slow, that is, it indicates where the unique values end, the problem arises exactly in this part of slow-to-back testing, the function is not returning me the exact value, wanted to make this test using the swap function().