Add decoding script
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@@ -18,63 +18,88 @@ def find_node(nodes, target_character):
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# if desired character not found, return empty list
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return []
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# retrieve text to encode
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txt = input("Text: ")
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def encode(txt):
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# create list of tuples in descending order of frequency: (character, frequency)
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info = Counter(txt).most_common()
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# change the list into ascending order
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info.reverse()
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# create list for character tuples
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nodes = []
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# create list for node usage frequencies
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frequencies = []
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# create list of tuples in descending order of frequency: (character, frequency)
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info = Counter(txt).most_common()
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# change the list into ascending order
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info.reverse()
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# create list for character tuples
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nodes = []
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# create list for node usage frequencies
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frequencies = []
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# copy nodes and their usage frequencies to the dedicated lists
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for item in info:
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nodes.append(item[0])
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frequencies.append(item[1])
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# copy nodes and their usage frequencies to the dedicated lists
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for item in info:
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nodes.append(item[0])
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frequencies.append(item[1])
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# repeat until only one top-level node exists
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while len(nodes) > 2:
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# combine two least frequent characters' nodes into a new tuple node, containing the old nodes (old_node_1, old_node_2)
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new_node = (nodes[0], nodes[1])
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# combine two least frequent characters' frequencies into a total frequency, to be used at the top level of the list of nodes
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new_frequency = frequencies[0] + frequencies[1]
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# remove nodes that have been nested inside the new node
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del nodes[0:2]
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# remove frequencies that have been summed and added to the new frequency
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del frequencies[0:2]
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# find index of last node with frequency below that of the new node
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# if the largest frequency is smaller than the new one, place the new node at the end of the list
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if (frequencies[-1] < new_frequency):
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i = -1
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else:
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# else, loop over every frequency
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for index, item in enumerate(frequencies):
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# if the frequency is greater than or equal to the new frequency
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if (item >= new_frequency):
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# record the index to insert the frequency at
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i = index
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# stop looping
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break
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# insert the new node in its rightful position, maintaining ascending order of frequency
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nodes.insert(i, new_node)
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# insert the new frequency in its rightful position, maintaining ascending order of frequency
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frequencies.insert(i, new_frequency)
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# repeat until only one top-level node exists
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while len(nodes) > 2:
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# combine two least frequent characters' nodes into a new tuple node, containing the old nodes (old_node_1, old_node_2)
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new_node = (nodes[0], nodes[1])
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# combine two least frequent characters' frequencies into a total frequency, to be used at the top level of the list of nodes
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new_frequency = frequencies[0] + frequencies[1]
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# remove nodes that have been nested inside the new node
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del nodes[0:2]
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# remove frequencies that have been summed and added to the new frequency
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del frequencies[0:2]
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# print all nodes
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print("Nodes: %s" % nodes)
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# encrypted text
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output = ""
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# for every character in the text to be encrypted
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for char in txt:
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# find its path and add it to the encrypted text
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output += "".join(find_node(nodes, char))
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# print encoded message
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print("Encoded message: %s" % output)
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# find index of last node with frequency below that of the new node
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# if the largest frequency is smaller than the new one, place the new node at the end of the list
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if (frequencies[-1] < new_frequency):
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i = -1
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else:
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# else, loop over every frequency
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for index, item in enumerate(frequencies):
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# if the frequency is greater than or equal to the new frequency
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if (item >= new_frequency):
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# record the index to insert the frequency at
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i = index
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# stop looping
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break
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# insert the new node in its rightful position, maintaining ascending order of frequency
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nodes.insert(i, new_node)
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# insert the new frequency in its rightful position, maintaining ascending order of frequency
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frequencies.insert(i, new_frequency)
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# return encoded message
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return [output, nodes]
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# print all nodes
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print("Nodes: %s" % nodes)
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def decode(txt, nodes):
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# string to hold decoded message
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output = ""
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# replicate nodes, for looping over and editing with the first part of the code
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node = nodes
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# for each digit
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for digit in txt:
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# get the node with the corresponding index
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node = node[int(digit)]
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# if the retrieved node isn't a tuple (i.e. it isn't a parent node)
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if (not isinstance(node, tuple)):
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# add the node's content to the output
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output += node
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# replace the retrieved node with the whole tree again, for looping over and editing with the next part of the code
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node = nodes
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# encrypted text
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output = ""
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# print decoded message
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print("Decoded message: %s" % output)
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# return decoded message
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return output
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# for every character in the text to be encrypted
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for char in txt:
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# find its path and add it to the encrypted text
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output += "".join(find_node(nodes, char))
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# print encrypted message
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print("Encrypted message: %s" % output)
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encoding = encode(input("Text: "))
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decode(encoding[0], encoding[1])
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