Oh. My. God. JEBUS! I ACed it! Just use suffix array + Kasai and it will work out just fine. Trust me :)

But also here is what I collected about test 30 :
* Size of the string = 250000.
* All letters of English alphabet are being used.
* If we divide the string into heterogeneous and homogeneous regions, then the latter forms a majority. Moreover, longest homogeneous region = 396 and heterogeneous = 6.
* The amount of divergent adjacent characters is between 5000 and 10000.

Hope it helps :3