Description

In this problem, students can use accounts to take online courses.

The program architecture is explained as follows.

 

A. Definition of class Student

• An abstract base class that declares pure virtual learn() method
• Has a string (note) used to record what the student learns
• Derived classes
  • InterestedStudent
    • Just note the latest thing
  • StrivingStudent
    • Note everything learned

 

B. Definition of class Account

• A node of doubly linked list

 

C. Definition of class OnlineCourse

• An abstract base class that declares pure virtual material() method
• Operator+= means login
  • A student can use an account to login an online course.
• Operator-= means logout
  • If a student has been taking an online course, he/she can logouts the online course.
• Derived classes
  • Math
    • The input will be a pre-order expression with +, -, *, /
    • material() method has to return the answer of the expression
  • English
    • The input will be a string
    • material() method has to separate the characters of the input string by new lines if a next character is uppercase

 

You are asked to implement

• void InterestedStudent::learn(const string &str)
  • The Student learns the material by saving the input str to the note.

• void StrivingStudent::learn(const string &str)

  • Note: if he/she learns something, you need to attach a new line and then the new material to the “note”.

• void OnlineCourse::operator+=(Student *s)

  • create an Account for the Student and insert the Account to the doubly linked list.

  • Note:

    • A student cannot login a same course for more than one time.

    • But a student can logout a course, and then login again.

• void OnlineCourse::operator-=(Student *s)

  • remove the Account for the Student from the doubly linked list and then delete the Account.

• string Math::material(istream &input)

• string English::material(istream &input)

  • Note: you don’t need to insert a new line before the first character, even if it’s uppercase.

 

 

Input

First line contains an integer n and n types from {m, e}

• Integer n means n online courses
• type m means Math
• type e means English

Second line contains an integer m and m types from {i, s}

• integer m means m students
• type i means InterestedStudent
• type s means StrivingStudent

and then, there are 4 kinds of commands

• i n m:

m-th student logins n-th course

• o n m:

m-th student logouts n-th course

• u n:

there are new input for n-th course

• s m:

show the note of m-th student

 

 

Output

the output depends on the input commands.

 

 

Sample Input  Download

Sample Output  Download

Partial Judge Code

11453.cpp

Partial Judge Header

11453.h

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