Let's pick up from where we left off on the
previous page. This is
the last page by the way!
if (left<j) {
quickSort(arrayInput, left, j);
}
if (i<right) {
quickSort(arrayInput, i, right);
}
Once you break out of the loop, you are presented with
two if statements. The first if statement checks to see if
the value stored by your left variable is less than j. If it
is, then you call your quickSort function again with the
left and right boundaries being the original vale for left
and the variable j.
The second if statement checks to see if i less than the
value stored by your right variable. If it is, then it calls
the quickSort function with the left and right boundaries
represented by your i and right variables respectively.
return;
This line of code is purely optional. If the data in your
function escaped the while loop and snuck past the above two
if statements, we simply end the function call. In Flash,
you do not have to specify return - exiting a function is
automatically taken care of when all other avenues for your
function to work are exhausted.
This return does not mean that all calls of the quickSort
function stop working. You may have many concurrent
quickSort functions sorting various portions of your
arrayInput if caught by the above two if statements. This
return statement exits only this particular instance of the
quickSort function.
Well, you have reached the end of this tutorial. There are
many ways to have described how quicksort works in a
fraction of the pages, but I really think the extra material
really helps in understanding the details of quicksort in a
relatively pain-free way!
For the most part, people will never know whether you
implemented your sort algorithm using quicksort. Did you
know that Flash's built-in array sort methods are a
variation of quicksort, and that they are also
faster? They are! Most sort methods in
modern languages is some form of quicksort, but I think by
understanding
how quicksort really works, you can better customize your
sort depending on the situation. You may not always have a
simple set of data in a list or array form.
There will be times when a built-in sort method is the
best solution to a problem. Every now and then, though, you
will run into a situation where what you are trying to sort
might not conform to the particular requirements of a
language's built-in sort function. For example, in a project
I was working on in C#, I was required to sort a massive
amount of data stored in a hashmap-like Dictionary object.
It was the solution to that, which I altered for Flash, that
prompted me to write this tutorial.
If you have a question about this or any other topic, the easiest thing is to drop by our forums where a bunch of the friendliest people you'll ever run into will be happy to help you out!
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This is a companion discussion topic for the original entry at http://www.kirupa.com/developer/actionscript/quickSort13.htm
