1.分别统计出其中英文字母数和空格数及整篇文章总字数； 2.统计某一字符串在文章中出现的次数，并输出该次数 3.删除某一子串，并将后面的字符前移(1. respectively, the statistics of the number of letters and spaces English number and the total number of words; 2. times a string statistics in the article, and outputs the number 3. to remove a substring, and behind the characters forward)