alternative for STL - sort(quick)

sort.cpp

// based on quick sort
template<typename T>
void sort(T *arr, T *end) {
    int l = 0, r = (end - arr) - 1;
    if (l >= r) return;
    T mid = arr[(l + r) / 2];
    while (l <= r) {
        while (arr[l] < mid) ++l;
        while (mid < arr[r]) --r;
        if (l <= r) {
            swap(arr[l++], arr[r--]);
        }
    }
    sort(arr, arr + l);
    sort(arr + l, end);
}