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41 lines
1.0 KiB
Python
41 lines
1.0 KiB
Python
def dencrypt(s: str) -> str:
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"""
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Performs ROT13 encryption/decryption on the input string `s`.
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https://en.wikipedia.org/wiki/ROT13
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>>> msg = "My secret bank account number is 173-52946 so don't tell anyone!!"
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>>> s = dencrypt(msg)
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>>> s
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"Zl frperg onax nppbhag ahzore vf 173-52946 fb qba'g gryy nalbar!!"
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>>> dencrypt(s) == msg
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True
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"""
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# Validate input
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assert isinstance(s, str), "Input must be a string"
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# Using list to accumulate characters for efficiency
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out = []
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for c in s:
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if "A" <= c <= "Z":
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out.append(chr(ord("A") + (ord(c) - ord("A") + 13) % 26))
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elif "a" <= c <= "z":
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out.append(chr(ord("a") + (ord(c) - ord("a") + 13) % 26))
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else:
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out.append(c)
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return "".join(out)
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def main() -> None:
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s0 = input("Enter message: ")
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s1 = dencrypt(s0)
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print("Encryption:", s1)
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s2 = dencrypt(s1)
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print("Decryption:", s2)
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if __name__ == "__main__":
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import doctest
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doctest.testmod()
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main()
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