int required = allRequired[requiredChosen];

    // ...do the first selection...
    selectInPlace(required, array, from, to);

    // ...then recursively perform the selections in the range below...
    int requiredBelow = requiredChosen - 1;
    while (requiredBelow >= requiredFrom && allRequired[requiredBelow] == required) {
      requiredBelow--; // skip duplicates of required in the range below