题解 | 小红背单词

n = int(input())
words = []#已经记住的单词
dic = dict()#要记得单词，以及背的次数
for i in range(n):
    word = input()
    dic[word] = dic.setdefault(word,0)+1#将当前背的单词，背的次数+1
    if word not in words and dic[word]==len(words)+1:#查看当前背的单词，是否满足记住的条件
        words.append(word)
print(len(words))#输出记住的单词