So, I learned that it is possible to implement IOI-style tasks on Codeforces by implementing a grader program.

The gist of the problem I want to set is: Given x, implement two functions encode(x) and decode(code) such that decode(encode(x)) == x. This is a pretty standard class of puzzles.

Unfortunately, if the participant submits one grader function, then it is possible for them to maintain a global map that just contains the actual exact answers for each x, and then cheese the problem this way.

I believe the way to get around this is to run all the encode steps in one run, and then run all the decode steps on a second run. My guess is that I can do this by ticking the following "Advanced Settings" box on Polygon:

Is this correct? If so, could someone be kind enough to please share me an example of a Polygon problem that does this, so I can see what I need to implement?