Analysis of an optimized search algorithm for skip lists

Abstract

It was suggested in Pugh (1990) to avoid redundant key comparisons in the skip list search algorithm by marking those elements whose key has already been compared against the search key. We present here a precise analysis of the total search cost (expectation and variance), where the cost of the search is measured in terms of the number of key-to-key comparisons. These results are then compared with the corresponding values of the standard search algorithm.