学生成绩计算的算法实现,根据Prerequisites题目编写完成的.-

Problem Statement

       

***Note:　Please keep programs under 7000 characters in length.　Thank you





Class Name: Prerequisites

Mathod Name: orderClasses

Parameters: String[]

Returns: String[]



You are a student at a college with the most unbelievably complex prerequisite

structure ever. To help you schedule your classes, you decided to put together

a program that returns the order in which the classes should be taken.　



Implement a class Prerequisites which contains a method orderClasses.　The

method takes a String[] that contains the classes you must take and returns a

String[] of classes in the order the classes should be taken so that all

prerequisites are met.



String[] elements will be of the form (and TopCoder will ensure this):

"CLASS: PRE1 PRE2 ..." where PRE1 and PRE2 are prerequisites of CLASS.　CLASS,

PRE1, PRE2, ... consist of a department name (3 or 4 capital letters, A-Z

inclusive) followed by a class number (an integer between