Pergunta de entrevista da empresa YouTube

-If a web page is taking time to load then how you will debug the problem? -Following problems she gave me to write a code for it. First she asked me the algorithm, then she asked me the time complexity.: Given a lists of strings, group them by last two letters. i.e. input : cat, top, bat, hop, rot, sat, food op: cat, bat, sat top, hop