class MinMaxWordFinder:
    def __init__(self):
        self.sp = []

    def add_sentence(self, word):
        self.sp += word.split()

    def shortest_words(self):
        min_len = min(self.sp, key=len)
        return list(filter(lambda x: len(x) == len(min_len), self.sp))

    def longest_words(self):
        max_len = max(self.sp, key=len)
        return list(filter(lambda x: len(x) == len(max_len), self.sp))