## L303 / kick off file
## SXD

''' 
Consider the following binary encoding of the alphabet A = {'a', 'b', 'c', 'd', 'e'}: 
'a' → '0', 'b' → '11', 'c'→ '100', 'd' → '1010', 'e' → '1011'.
'''
R = [('a','0'), ('b','11'), ('c','100'), ('d','1010'), ('e','1011')]

# encoding dictionary
x2c = dict(R)

# decoding dictionary
c2x = dict([(c,x) for x, c in R])


''' 1.
Define a function E(X) that yields, given a message X in the alphabet A, 
the encoded message. For example, E("aac") should yield '001011'.
'''

def E(X):
    return 
    
''' 2.
Generate a random message X of length 50 (say) in the alphabet A 
with expected frequences 50, 20, 15, 10 and 5 for the characters 
'a', 'b', 'c', 'd', 'e' and find the coded message C.
'''



''' 3.
In an ASCII-like encoding the message X requires at least 3 bits per character. 
Find how many bits per character are needed for the encoding C. 
What is the compression ratio?
'''



''' 4.
Define a function D(C) that yields, given an encoded message C, 
the original message X. Test it with the C obtained in the previous point.
'''