mirror of
https://github.com/TheAlgorithms/Python.git
synced 2024-12-25 12:40:14 +00:00
4fb978cf58
2. Corrected Logic {AVL.py, 104-107}
3. Removed unnecessary semicolons {BellmanFord.py, Dijkstra.py}
103 lines
2.8 KiB
Python
103 lines
2.8 KiB
Python
import string
|
|
import itertools
|
|
|
|
def chunker(seq, size):
|
|
it = iter(seq)
|
|
while True:
|
|
chunk = tuple(itertools.islice(it, size))
|
|
if not chunk:
|
|
return
|
|
yield chunk
|
|
|
|
|
|
|
|
def prepare_input(dirty):
|
|
"""
|
|
Prepare the plaintext by up-casing it
|
|
and separating repeated letters with X's
|
|
"""
|
|
|
|
dirty = ''.join([c.upper() for c in dirty if c in string.ascii_letters])
|
|
clean = ""
|
|
|
|
if len(dirty) < 2:
|
|
return dirty
|
|
|
|
for i in range(len(dirty)-1):
|
|
clean += dirty[i]
|
|
|
|
if dirty[i] == dirty[i+1]:
|
|
clean += 'X'
|
|
|
|
clean += dirty[-1]
|
|
|
|
if len(clean) & 1:
|
|
clean += 'X'
|
|
|
|
return clean
|
|
|
|
def generate_table(key):
|
|
|
|
# I and J are used interchangeably to allow
|
|
# us to use a 5x5 table (25 letters)
|
|
alphabet = "ABCDEFGHIKLMNOPQRSTUVWXYZ"
|
|
# we're using a list instead of a '2d' array because it makes the math
|
|
# for setting up the table and doing the actual encoding/decoding simpler
|
|
table = []
|
|
|
|
# copy key chars into the table if they are in `alphabet` ignoring duplicates
|
|
for char in key.upper():
|
|
if char not in table and char in alphabet:
|
|
table.append(char)
|
|
|
|
# fill the rest of the table in with the remaining alphabet chars
|
|
for char in alphabet:
|
|
if char not in table:
|
|
table.append(char)
|
|
|
|
return table
|
|
|
|
def encode(plaintext, key):
|
|
table = generate_table(key)
|
|
plaintext = prepare_input(plaintext)
|
|
ciphertext = ""
|
|
|
|
# https://en.wikipedia.org/wiki/Playfair_cipher#Description
|
|
for char1, char2 in chunker(plaintext, 2):
|
|
row1, col1 = divmod(table.index(char1), 5)
|
|
row2, col2 = divmod(table.index(char2), 5)
|
|
|
|
if row1 == row2:
|
|
ciphertext += table[row1*5+(col1+1)%5]
|
|
ciphertext += table[row2*5+(col2+1)%5]
|
|
elif col1 == col2:
|
|
ciphertext += table[((row1+1)%5)*5+col1]
|
|
ciphertext += table[((row2+1)%5)*5+col2]
|
|
else: # rectangle
|
|
ciphertext += table[row1*5+col2]
|
|
ciphertext += table[row2*5+col1]
|
|
|
|
return ciphertext
|
|
|
|
|
|
def decode(ciphertext, key):
|
|
table = generate_table(key)
|
|
plaintext = ""
|
|
|
|
# https://en.wikipedia.org/wiki/Playfair_cipher#Description
|
|
for char1, char2 in chunker(ciphertext, 2):
|
|
row1, col1 = divmod(table.index(char1), 5)
|
|
row2, col2 = divmod(table.index(char2), 5)
|
|
|
|
if row1 == row2:
|
|
plaintext += table[row1*5+(col1-1)%5]
|
|
plaintext += table[row2*5+(col2-1)%5]
|
|
elif col1 == col2:
|
|
plaintext += table[((row1-1)%5)*5+col1]
|
|
plaintext += table[((row2-1)%5)*5+col2]
|
|
else: # rectangle
|
|
plaintext += table[row1*5+col2]
|
|
plaintext += table[row2*5+col1]
|
|
|
|
return plaintext
|