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 setter only makes one grader file, and the participant submits one file with the implemented functions, 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?