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.

Debugged Insertion sort 47

What happened?  Turns out I used
"> =" instead of ">=". 

The whole thing dies.
The perfect one-liner game  is not for everyone......

Insertion sort 45 -47 (perl one-liner)

Ah, it got me.   45 and 46 both failed first time.  Debugging one-liner needs to make sure bracket matches mentally.  (It's difficult.) I even found that I can't debug insertion sort 47.  Since the machine is suddenly halt.

Bummer for the day, I guess this is skill.  You got to fail sometime to refine it.

Insertion sort 43 (perl one-liner)

:) Quite epic. 

perl -lane '{push @A,$_}END{for($j=1;$j<$#A+1;$j++){$k=$A[$j];$i=$j-1;while($i>=0&&$A[$i]>$k){$A[$i+1]=$A[$i];$i--}$A[$i+1]=$k;} printf("%s\n",join(" ",@A))}'

33_P

36th writing of insertion sort(C)

Good.  33_P

33rd writing of insertion sort (C)

Nailed it. Feel more natural.  It's better to time myself from now on.
33_P

30th writing of insertion sort (perl)

Got it right. Checking mentally is important.
33_P

29th writing of insertion sort (perl)

Still got it wrong.  Changed > to = in the second condition.  Should spot-check every condition before interpretation.

21st time of insertion sort writing(C)

Get it right.

This makes you compare program writing as playing an Arcade shooting game.  Equally difficult but equally understated.

33_P

17-19th writings of insertion sort (C)

Had lunch, try again. 

17th: missed i=j-1;
18th: when print, print i instead of A[i].  Wow 3rd time.
19th: get it right.

That's why not many people can treat programming as arcade.  Even a simple game like insertion sort is not easy to play.
33_P

17th writing of insertion sort (C)

Get it right the first time.

Of course, all these writings are all start from scratch.   It's like you retype a command.

Another discovery: these kinds of practice doesn't take time at all. Why not?