  When the search algorithm QuickSelect compares keys during its execution in
order to find a key of target rank, it must operate on the keys'
representations or internal structures, which were ignored by the previous
studies that quantified the execution cost for the algorithm in terms of the
number of required key comparisons. In this paper, we analyze running costs for
the algorithm that take into account not only the number of key comparisons but
also the cost of each key comparison. We suppose that keys are represented as
sequences of symbols generated by various probabilistic sources and that
QuickSelect operates on individual symbols in order to find the target key. We
identify limiting distributions for the costs and derive integral and series
expressions for the expectations of the limiting distributions. These
expressions are used to recapture previously obtained results on the number of
key comparisons required by the algorithm.
