Create a Program to Create Caesar Cipher in C++ Assignment Solution.

def main():

# Define the alphabet

alphabet = 'abcdefghijklmnopqrstuvwxyz'

# Now, ask user for letter code and number

while True:

code = input("Enter letter code: ")

code = code.lower()

if code in alphabet:

break

else:

print("Please enter a letter from the alphabet.")

# Ask for number

while True:

N = input("Enter number (shift): ")

if N.isnumeric():

N = int(N)

break

else:

print("Please enter a valid number.")

# Now, construct the key by right-shifting the alphabet N positions starting at code

code_index = alphabet.index(code) # Index of the letter code

encoded_index = code_index + N # Index of the letter to substitute the letter code

# If the new index is higher than the length of the alphabet, then subtract the len of the alphabet from that index

# This will make the alphabet to be arranged in a circle

if(encoded_index > len(alphabet)-1):

encoded_index = len(alphabet) - 1 - encoded_index

# Encoded letter

encoded_letter = alphabet[encoded_index]

# Construct dict with key

# For a letter code 'A' and a shift of 3, the dictionary will contain the following items

# {'a': 'd', 'b': 'e', 'c', 'f', 'd': 'g', ...}

key = dict()

i = 0

# Now, loop through the alphabet and assign the encoded letter in the dictionary

for letter in alphabet:

key[letter] = alphabet[encoded_index]

encoded_index += 1

if(encoded_index > len(alphabet)-1):

encoded_index = 0

"""

UNCOMMENT THE FOLLOWING LINE IF YOU WANT TO SEE THE DICTIONARY WITH THE KEY OF THE CIPHER

"""

# print(key)

# Now, ask user for string to encode

text = input("Entet text to encode: ")

# Encode

encoded_text = encode(text, key)

# Decode

decoded_text = decode(encoded_text, key)

print("")

print("The encoded text is: " + encoded_text)

print("")

print("The decoded text is: " + decoded_text)

def encode(text, key):

"""

Given a text and a dictionary containing a key, this function returns an encoded version of text

:param text: Text to encode

:param key: Dictionary containing the key

return: Encoded text

"""

encoded_text = ""

for c in text: # Loop through each char in the text

c_l = c.lower() # Convert it to lower case

if c_l in key: # Check if the character is in the alphabet

c_coded = key[c_l] # code

if c.isupper(): # check if the original character is upper case

c_coded = c_coded.upper()

encoded_text += c_coded

else: # The character is not in the alphabet. Probably a sign of exclamation, a comma, etc

encoded_text += c

return encoded_text

def decode(text, key):

"""

Given a text and a dictionary containing a key, this function returns a decoded version of text

:param text: Encoded text

:param key: Dictionary containing the key

:return: Decoded version of text

"""

# We have to reverse the dictionary containing the key

key = {value: k for (k, value) in key.items()}

decoded_text = ""

for c in text: # Loop through each char in the text

c_l = c.lower() # Convert it to lower case

if c_l in key: # Check if the character is in the alphabet

c_coded = key[c_l] # decode

if c.isupper(): # check if the original character is upper case

c_coded = c_coded.upper()

decoded_text += c_coded

else: # The character is not in the alphabet. Probably a sign of exclamation, a comma, etc

decoded_text += c

return decoded_text

if __name__ == '__main__':

main()