Java Homework Help - Recursion with array

Question

I've got a set of recursion problems that I need to do. I've completed 3 out of the 4 of them we were given, but I'm having a hard time wrapping my head around this last one. I don't necessarily want the actual answer, but maybe just point me in the right direction, because I'm not even seeing what my stop condition should be on this one. And note, it has to be recursive, no loops, etc.

Thanks in advance for any help provided!

Write recursive method arrayRange that returns the maximum integer minus the minimum integer in the filled array of ints. Use recursion; do not use a loop. The following assertions must pass (note the shortcut way to pass a reference to a new array--it saves your writing a bit of code (this passes an array built as a parameter):

assertEquals(2, rf.arrayRange(new int[] { 1, 2, 3 } ));

assertEquals(2, rf.arrayRange(new int[] { 3, 2, 1 } ));

assertEquals(0, rf.arrayRange(new int[] { 3 } ));

assertEquals(3, rf.arrayRange(new int[] { -3, -2, -5, -4 } ));

// Precondition: a.length > 0 public int arrayRange(int[] a)

True! And the OP does not want a straight up answer but help. — gideon
– gideon, Commented Mar 26, 2011 at 6:43

user166390 · Accepted Answer · 2011-03-26 06:42:41Z

2

The stop condition is when there are only two items left: the maximum and minimum. Then just return the difference. (Also handle the case of 1 or 0 items, consider input such as in the test cases.)

Now .. how to reduce the list each pass? :) I would consider inspecting the first three values at a time (of the three, only two should remain in the recursive step).

Happy homeworking.

answered Mar 26, 2011 at 6:42

user166390

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3 Comments

user677786 Over a year ago

That makes total sense now that you put it like that. Thanks a bunch! Gonna get to working on that solution. Should I post the solution when I get it or is that a bad idea?

user166390 Over a year ago

@user677786 If you do wish to post a solution here, consider updating your original post (with a disclaimer/warning that your solution is below: it might take away the fun for someone else though!). I'd at least wait until after the assignment is due ;-)

user677786 Over a year ago

Ok, got it figured out :P I'll post the solution after the due date :P Thanks again!

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