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