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97 lines
3.1 KiB
Python
97 lines
3.1 KiB
Python
#!/usr/bin/env python3
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"""
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A Polybius Square is a table that allows someone to translate letters into numbers.
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https://www.braingle.com/brainteasers/codes/polybius.php
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"""
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import numpy as np
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class PolybiusCipher:
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def __init__(self) -> None:
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SQUARE = [
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["a", "b", "c", "d", "e"],
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["f", "g", "h", "i", "k"],
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["l", "m", "n", "o", "p"],
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["q", "r", "s", "t", "u"],
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["v", "w", "x", "y", "z"],
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]
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self.SQUARE = np.array(SQUARE)
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def letter_to_numbers(self, letter: str) -> np.ndarray:
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"""
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Return the pair of numbers that represents the given letter in the
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polybius square
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>>> np.array_equal(PolybiusCipher().letter_to_numbers('a'), [1,1])
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True
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>>> np.array_equal(PolybiusCipher().letter_to_numbers('u'), [4,5])
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True
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"""
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index1, index2 = np.where(self.SQUARE == letter)
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indexes = np.concatenate([index1 + 1, index2 + 1])
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return indexes
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def numbers_to_letter(self, index1: int, index2: int) -> str:
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"""
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Return the letter corresponding to the position [index1, index2] in
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the polybius square
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>>> PolybiusCipher().numbers_to_letter(4, 5) == "u"
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True
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>>> PolybiusCipher().numbers_to_letter(1, 1) == "a"
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True
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"""
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letter = self.SQUARE[index1 - 1, index2 - 1]
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return letter
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def encode(self, message: str) -> str:
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"""
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Return the encoded version of message according to the polybius cipher
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>>> PolybiusCipher().encode("test message") == "44154344 32154343112215"
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True
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>>> PolybiusCipher().encode("Test Message") == "44154344 32154343112215"
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True
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"""
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message = message.lower()
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message = message.replace("j", "i")
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encoded_message = ""
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for letter_index in range(len(message)):
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if message[letter_index] != " ":
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numbers = self.letter_to_numbers(message[letter_index])
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encoded_message = encoded_message + str(numbers[0]) + str(numbers[1])
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elif message[letter_index] == " ":
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encoded_message = encoded_message + " "
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return encoded_message
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def decode(self, message: str) -> str:
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"""
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Return the decoded version of message according to the polybius cipher
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>>> PolybiusCipher().decode("44154344 32154343112215") == "test message"
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True
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>>> PolybiusCipher().decode("4415434432154343112215") == "testmessage"
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True
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"""
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message = message.replace(" ", " ")
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decoded_message = ""
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for numbers_index in range(int(len(message) / 2)):
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if message[numbers_index * 2] != " ":
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index1 = message[numbers_index * 2]
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index2 = message[numbers_index * 2 + 1]
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letter = self.numbers_to_letter(int(index1), int(index2))
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decoded_message = decoded_message + letter
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elif message[numbers_index * 2] == " ":
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decoded_message = decoded_message + " "
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return decoded_message
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