Finally, Bender et al did not address that their approach
takes worst case O(j + n) operations to perform
select(j;A), which finds the j-th smallest element in an
array A. This is because the j-th smallest element does not
locate at A[j-1]. It locates at somewhere between A[j-1]
to A[j - 1 + j=n] depending on the distribution of the
gaps. Without knowing the location of the gaps, a linear
scan is required to determine the rank of the j-th smallest
element between insertions. It is possible to improve
select by using more space to maintain the locations of
gaps, using a similiar structure like the weight-balanced
B-tree by Dietz (Dietz 1989).