When that problem came out I solved it quickly (it was 1 million 8 digit numbers in sorted in 1MB of RAM, which I think is the original problem that gained noto

When that problem came out I solved it quickly (it was 1 million 8 digit numbers in sorted in 1MB of RAM, which I think is the original problem that gained notoriety) with basically arithmetic compression of the delta stream, since the number of possible states sits decently inside the required RAM. I also saw I can sort it it using zero bytes of storage using a lot of code :) Think nested switches that eventually print a lot of numbers.