'''
CSCI 204.01 Exam 1 review exercise
Divide the students into groups and each group solves one proble, then exchange their ideas
or solution.
1. Write a Python function that can remove a node with specific data value in a doubly linked list.
2. Write a Python function that can count the number of nodes in a circular linked list with a specific data value.
3. Write an operator overloading function __sub__ that removes a node with specified value in a singly linked list.
4. Write a recursive function to compute the length of a singly linked list.
5. Write a child class with a constructor, string function, length function that inherits information from a parent class.
'''

'''
This is the start file for P1 and P4 (singly linked list
'''
class UserList:
    def __init__(self):
        self.head = None
        self.tail = None

    def insert_after(self, data):
        """ Insert a node with data at the end of the list
        """
        node = ListNode(data)
        if self.is_empty():   # the node will be the first one in list
            self.head = node
            self.tail = node
        else:                 # insert after the current tail
            self.tail.next = node
            self.tail = node


    def is_empty(self):
        """ Return True if the list is empty, False otherwise.
        """
        return self.head == None

    def __sub__(self, rhs_node):
        """Overload the operator '-' so that l = l - node is valid"""
        pass

    def remove_all(self, value):
        """Remove all nodes with given value in the list"""
        pass
            
class ListNode:
    """ The node class for list notes"""
    def __init__(self, data):
        self.data = data
        self.next = None