I passed all but one testcase. Its the ninth basic testcase, and it says: '\n\n' should equal '\n'. Other than that idk what else, does anyone have an idea as to what might cause this? or what might I be doing wrong? If anyone wants to see my code, im more than happy to show you somewhere else.

i agree with what has been said and ill keep that in mind next time. But also to make it faster, could you also add a break right after you add the element into the set. Because elements in a1 needs to be a substring of at least one of the elements in a2, wouldnt it be best to cut off the for-loop and go on with the next word in a1?

im new to coding and im curious, i like to make my code as optimal as possible :)