Shell sort

In programming drilling, I am still in the process of groking insertion sort.  Insertion sort can be thought as a combination of two operations.  1) find the place to insert. 2) shift.   In fact these two operations are more general patterns which in actual programming that appears most.   These two basic operations is not entirely trivial.  Or else there won't be tricks just to improve one single aspect.  e.g. Binary insertion sort is trying to improve how you find the place to insert.   Using tricks like memmove and linked-list means you shift faster.

I still don't think I grok insertion sort. Shell and library sort are the two ideas I want to drill it.   They are deep concept.  That might mean I need to set it aside and call it Read 4 in future.

I also read Sedgewick's survey paper on Shell sort.   It's interesting to read and the fun part is that I think I understand the argument.   This is likely because my background of having read "Elementary Number Theory".  (It's a great self-learning book by the way.)  I guess I will some time to drill on it until I grok.