Wraparound Arrays?

Hi There!

Something really simple I need an answer for. I already wrote a code that solves my problem, but it somehow looks stupid (lots of if's, compares and stuff). I'm sure that there is a simpler way..

The problem is: I have an array.. The array itself forms a circular ring. In other words: The elements [n] and [n+1] are near to each other.. Same as [n] and [n-1].

Because the ring is circular the elements [0] and [size-1] are also neighbours.

Now my question: I need to find the distance of two indices in the ring.. The only thing that's difficult here is the wrap-around from Size-1 to 0. Obviously there are two different distances (you can go either way around the ring). I'm only interested in the smaller one.

Also it would be nice to find out which direction (incrementing indices or decrementing indices) is the shorter.

Prototype of my function would look like this:

int DistenceOfIndices (int a, int b);

You can of cause consider that the size of the array is known.. a variable called ArraySize holds the number of elements.

Ok folks.. This is really a simple one, and I would like to see your ideas of a clever algorithm to find out that sort of things. brute force counting is not a good idea btw. I'm calling this function _lots_ of time on a very slow cpu.


Last sidenode:

Even if I speak about circular rings it doesn't mean that the array forms a real circle. it's just that the last and first elements are connected. nothing more, and nothing less.


Thanks,
  Nils Pipenbrinck



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