'''
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 all nodes with a specific value in a singly 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 doubly linked list.
5. Write a child class with a constructor and string function that inherits information from a parent class.
'''

'''
This file contains solutions to P2
'''
class CircularListSingly:
    """A user defined singly linked circular list"""
    def __init__(self):
        self.ref = None    # self.ref always points to the end of the list
                           # alternatively we could have it point to the first
    def __str__(self):
        """ String function """
        s = '['
        h = self.ref
        if h == None:
            return '[]'
        else:
            temp_ref = h
            h = h.next
            s += '(ref) ' + str(h.data)
            while h != temp_ref:
                h = h.next
                if h != temp_ref:
                    s += ', '
                    s += str(h.data)
            s += ', '
            s += str(temp_ref.data)

        s += ']'
        return s
    
    def insert(self, node):
        """ Insert a node with value"""

        if self.ref == None:       # empty list
            self.ref = node
            node.next = self.ref
        else:                       # insert after ref
            node.next = self.ref.next
            self.ref.next = node

    def count_values(self, value):
        """Count all nodes containing a specific value"""
        count = 0
        node = self.ref
        if node == None:
            return 0
        while node.next != self.ref:
            if node.data == value:
                count += 1
            node = node.next
        return count
    
class ListNode:
    """ The node class for list notes"""
    def __init__(self, data):
        self.data = data
        self.next = None