里面涉及了好几个截取字符串的小函数。比如：一个字符在字符串出现的次数，或者某个字符第几次出现的位置。界面很潦草。主要看代码。-Which involves several small function string interception. For example: a character in a string of occurrences, or how many times a character appears. The interface is very scratchy. Main