In my opinion the min and max functions are overkill. But interesting solution.

Sneaky tests in python: some tests were lists of strings representing numbers, but some were lists of plain numbers.

Is it more efficient removing the duplicates this way or is it better with a set

Agree. The directions say to zero-pad, but the test results indicate to test for zero-padded numbers as unpadded.

Good kata. Was it a difficult programming challenge? Not really. Did it make me think of real world requirements and applications? Yes. Still an opportunity for good coding practices along the way.

Great comments! I came up with the same logic, but you explained it far more clearly with the comments and variable names.

principle of inclusion-exclusion to avoid double counting. very nice