Improved Shellsort for the Worst-Case, the Best-Case and a Subset of the Average-Case Scenarios

Sorting involves rearrangement of items into ascending or descending order. There are several sorting algorithms but some are more efficient than others in terms of speed and memory utilization. Shellsort improves on Insertion sort by decreasing the number of comparisons made on the items to be sorted. This paper presents an Improved Shellsort algorithm that further decreases the number of comparisons made on the items to be sorted through a modified diminishing increment sort. The results obtained from the implementation of both Shellsort and the proposed algorithm shows that the proposed algorithm has a fewer number of comparisons made for all input sizes of the best and worst cases and for input size of twenty or less for the average case. By implication, this means that the proposed algorithm is faster in these situations. The strength of the algorithm however diminishes for only the average case of input size greater than twenty