# COPYRIGHT 2019, Vida Dujmovic. All rights reserved.
# Any unauthorised distribution will constitute an infringement of copyright.


def read_raw(file):
    '''str->list of str
    Returns a list of strings that was stored in a file.'''
    raw = open(file).read().splitlines()
    for i in range(len(raw)):
        raw[i]=raw[i].strip()
    return raw


def clean_up(l):
    '''list of str->list of str

    The functions takes as input a list of characters.
    It returns a new list containing the same characters as l except that
    one of each characters that appears odd number of times in l is removed
    and all the * characters are removed

    >>> clean_up(['A', '*', '$', 'C', '*', '*', 'P', 'E', 'D', 'D', '#', 'D', 'E', 'B', '$', '#'])
    ['#', '#', '$', '$', 'D', 'D', 'E', 'E']

    >>> clean_up(['A', 'B', '*', 'C', '*', 'D', '*', '*', '*', 'E'])
    []
    '''

    clean_board=[]

    l=sorted(l) # O(n log n)
    #print(l)
    i=0
    while i<len(l)-1: # O(n)
        card1=l[i]
        card2=l[i+1]
        if card1==card2 and card1!='*': #discovered pair of same cards
            clean_board.append(card1)
            clean_board.append(card2)
            i=i+1           
        else: # do not copy this one. It is the odd card
            pass
        i=i+1
    return clean_board
    


def is_rigorous(l):
    '''list of str->bool
    Returns True if every character in the list appears exactlly 2 times or the list is empty.
    Otherwise, it returns False.

    Precondition: You may assume that every element in the list appears even number of times
    (i.e. that the list is clean-up by clean_up function)

    >>> is_rigorous(['E', '#', 'D', '$', 'D', '$', 'E', '#'])
    True
    >>> is_rigorous(['A', 'B', 'A', 'A', 'A', 'B'])
    False
    '''

    if len(l)==0: return True
    
    l=sorted(l) # O(n log n)
    for i in range(len(l)-2): # O(n)
        if l[i]==l[i+2]: # l[i] appears at least 3 times in the list
            return False
    return True
    
#main
file=input("Enter the name of the file: ")
file=file.strip()
b=read_raw(file)
print("\nBefore clean-up:\n", b)
b=clean_up(b)
print("\nAfter clean-up:\n", b)
if is_rigorous(b):
    print("\nThis list is now rigorous; it has no * and it has "+str(len(b))+" characters.")
else:
    print("\nThis list has no * but is not rigorous and it has "+str(len(b))+" characters.")