What was the optimal solution for these?\n\nQuestion1:\n\nGiven an array of strings "sentences", and an array of strings "usernames", find how many times each username appeared in total across all the sentences.\n\nQuestions2:\n\nGiven an array of strings "words", remove each word from the array that is a prefix of another word.

What was the optimal solution for these?\n\nQuestion1:\n\nGiven an array of strings "sentences", and an array of strings "usernames", find how many times each u