specific quick sort implementation in C++ for a struct based array

quicksort.cpp

void quickSort(wordItem arr[], int length, bool reverse) {
    if (length <= 1) {
        return;
    }
    const int pivot_count = arr[length / 2].count;
    int smaller_length = 0;
    int bigger_length = 0;
    int equal_length = 0;

    for (int i = 0; i < length; i++) {
        if (!reverse) {
            if (arr[i].count < pivot_count) smaller_length++;
            if (arr[i].count > pivot_count) bigger_length++;
        } else {
            if (arr[i].count > pivot_count) smaller_length++;
            if (arr[i].count < pivot_count) bigger_length++;
        }
        if (arr[i].count == pivot_count) equal_length++;
    }

    auto smaller = new wordItem[smaller_length];
    auto bigger = new wordItem[bigger_length];
    auto equal = new wordItem[equal_length];

    int smaller_i = 0;
    int bigger_i = 0;
    int equal_i = 0;

    // comparisons, this part should be pluggable to make this generic
    for (int i = 0; i < length; i++) {
        if (!reverse) {
            if (arr[i].count < pivot_count) smaller[smaller_i++] = arr[i];
            if (arr[i].count > pivot_count) bigger[bigger_i++] = arr[i];
        } else {
            if (arr[i].count > pivot_count) smaller[smaller_i++] = arr[i];
            if (arr[i].count < pivot_count) bigger[bigger_i++] = arr[i];
        }
        if (arr[i].count == pivot_count) equal[equal_i++] = arr[i];
    }

    quickSort(smaller, smaller_length, reverse);
    quickSort(bigger, bigger_length, reverse);

    int j = 0;
    // now overwrite the original array with:
    // smaller + equal + bigger

    for (int i = 0; i < smaller_length; i++) arr[j++] = smaller[i];
    for (int i = 0; i < equal_length; i++) arr[j++] = equal[i];
    for (int i = 0; i < bigger_length; i++) arr[j++] = bigger[i];
}