There are a couple aspects to this question that make it an awkward example for the site and a better fit for Stack Overflow.
First off, there was a good deal of original code in the question and the question was about that implementation.
I was implementing and testing out a simple insertion_sort:
The asked question was why a particular line of code should work one way or another:
it seems work, but when I do this little modification:
arr[j++] = arr[j];
the algorithm go in loop, so what's the point of difference with j+1 j++ and ++j in this case?(this last two I know their effect, but the first(j+1) in what differentiate from the other two incrementations?)
I want to emphasize the last bit:
so what's the point of difference with j+1 j++ and ++j in this case? (emphasis mine).
This question is not one about the higher level concepts of software design and architecture, but rather why a particular bit of code is behaving one way or another. That strongly biases the question to Stack Overflow being the proper place for the question to be on topic. That Stack Overflow has a good canonical duplicate for the question makes it a cleaner process to migrate it and duplicate it to the proper question that explains it very well.
The "Stack Overflow vs Programmers" really boils down to a quote that I am quite fond of.
Picture Programmers like a small conference room with a whiteboard. No computer, no books, no papers. You write your question on the whiteboard and experts walk by. Someone sees one that they can answer, they stop in and help.
The whiteboard lacks a compiler and a debugger. If the question starts getting to that level of specificity needed, then the question is likely a much better fit for Stack Overflow than Programmers.SE.
On the other hand if you're sketching up data models, and dare I say UML, or have a squiggly circle with "the cloud" in it, it is a question that Stack Overflow doesn't deal with (it lacks a specific implementation or debugging issue) and is much more in line with the "questions of software design and architecture" that are on topic on Programmers.SE.