Implementing a basic predator-prey simulation

Question

I am trying to implement a predator-prey simulation, but I am running into a problem. A predator searches for nearby prey, and eats it. If there are no near by prey, they move to a random vacant cell.
Basically the part I am having trouble with is when I advanced a "generation."
Say I have a grid that is 3x3, with each cell numbered from 0 to 8.
If I have 2 predators in 0 and 1, first predator 0 is checked, it moves to either cell 3 or 4
For example, if it goes to cell 3, then it goes on to check predator 1. This may seem correct but it kind of "gives priority" to the organisms with lower index values.. I've tried using 2 arrays, but that doesn't seem to work either as it would check places where organisms are but aren't. ._.
Anyone have an idea of how to do this "fairly" and "correctly?"

Answer 1

I recently did a similar task in Java. Processing the predators starting from the top row to bottom not only gives "unfair advantage" to lower indices but also creates patterns in the movement of the both preys and predators.

I overcame this problem by choosing both row and columns in random ordered fashion. This way, every predator/prey has the same chance of being processed at early stages of a generation.

A way to randomize would be creating a linked list of (row,column) pairs. Then shuffle the linked list. At each generation, choose a random index to start from and keep processing.