uniq array in-place

uniq_array.cpp

#include <iostream>
using std::cout;
using std::endl;

#include <vector>
using std::vector;

#include <algorithm>
using std::swap;

#include <concepts>
using std::is_swappable_v;
using std::equality_comparable;

template<typename T>
requires equality_comparable<T> && is_swappable_v<T>
typename vector<T>::size_type uniq_array(vector<T>& array) {
    typename vector<T>::size_type k = array.size() - 1;
    typename vector<T>::size_type j = 0;
    for (; j <= k; j += 1) {
        for (typename vector<T>::size_type i = j + 1; i <= k; i += 1) {
            if (array[j] == array[i]) {
                while (array[j] == array[k] && i <= k) {
                    k -= 1;
                }
                if (i <= k) {
                    if (i != k) {
                        swap(array[i], array[k]);
                    }
                    k -= 1;
                }
            }
        }
    }
    return j;
}

int main(void) {
    vector<int> a{1,1,1,2,2,1,1,1};
    vector<int>::size_type array_size = uniq_array(a);
    for (vector<int>::size_type i = 0; i < array_size; i += 1) {
        cout << a[i] << endl;
    }
    return 0;
}