ShellSort.h

template<typename T>
void shell_sort(T array[], int length) {
    int h = 1;
    while (h < length / 3) {
        h = 3 * h + 1;
    }
    while (h >= 1) {
        for (int i = h; i < length; i++) {
            for (int j = i; j >= h && array[j] < array[j - h]; j -= h) {
                std::swap(array[j], array[j - h]);
            }
        }
        h = h / 3;
    }
}