文件操作与字符处理，统计文本文件“case1.in”中的文章每个单词出现的次数（按出现次数由多到少的顺序输出，次数相同时按字典顺序输出，不足5个单词时，按序输出全部单词）-File manipulation and character processing, statistical text file " case1.in" in the article the number of occurrences of each word (number of occurrences