Posting List 소팅시 quickSort 사용

  private static final void quickSort(Posting[] postings, int lo, int hi) {
    if (lo >= hi)
      return;

    int mid = (lo + hi) / 2;

    if (postings[lo].term.compareTo(postings[mid].term) > 0) {
      Posting tmp = postings[lo];
      postings[lo] = postings[mid];
      postings[mid] = tmp;
    }

    if (postings[mid].term.compareTo(postings[hi].term) > 0) {
      Posting tmp = postings[mid];
      postings[mid] = postings[hi];
      postings[hi] = tmp;

      if (postings[lo].term.compareTo(postings[mid].term) > 0) {
        Posting tmp2 = postings[lo];
        postings[lo] = postings[mid];
        postings[mid] = tmp2;
      }
    }

    int left = lo + 1;
    int right = hi - 1;

    if (left >= right)
      return;

    Term partition = postings[mid].term;

    for (; ;) {
      while (postings[right].term.compareTo(partition) > 0)
        --right;

      while (left < right && postings[left].term.compareTo(partition) <= 0)
        ++left;

      if (left < right) {
        Posting tmp = postings[left];
        postings[left] = postings[right];
        postings[right] = tmp;
        --right;
      } else {
        break;
      }
    }

    quickSort(postings, lo, left);
    quickSort(postings, left + 1, hi);
  }