iCarnegie课程上的SSD1的一个练习，要求做完Catfish的源代码的exercise。需要的可以看看。写的不好，别见怪。-iCarnegie courses SSD1 a practice to require the source code Catfish finish the exercise. Need to look at. Write well,别见怪.

软件工程 SSD1 exercise1-For SSD1 exercise1 of Software Engineering