函数的功能是把字符串中的内容逆置。 例子如：字符串中原有的内容为：abcdefg，则调用该函数后，串中的内容为：gfedcba-Function is the function of the contents of the string against the home. Examples such as: Some of the contents of the Central Plains as a string: abcdefg, then call the function, the