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  1. def decipher(ciphertext: str, known_word: str) -> str:
  2.     """
  3.     Decrypts Caesar cipher by testing all possible shifts.
  4.     Returns first decryption containing the exact known_word or 'levalid' if not found.
  5.  
  6.     Args:
  7.         ciphertext: Encrypted text to decode
  8.         known_word: Exact word expected in plaintext (case-sensitive)
  9.  
  10.     Returns:
  11.         Decrypted text or 'levalid' if no valid decryption found
  12.     """
  13.  
  14.     def shift_char(c: str, shift: int) -> str:
  15.         """Shift character backward in alphabet by given positions"""
  16.         if c.islower():
  17.             return chr((ord(c) - ord('a') - shift) % 26 + ord('a'))
  18.         if c.isupper():
  19.             return chr((ord(c) - ord('A') - shift) % 26 + ord('A'))
  20.         return c  # Non-alphabetic unchanged
  21.  
  22.     # Test all possible shifts (0-25)
  23.     for shift in range(26):
  24.         decrypted = ''.join(shift_char(c, shift) for c in ciphertext)
  25.         if known_word in decrypted.split():  # Check as whole word
  26.             return decrypted
  27.  
  28.     return "levalid"
  29.  
  30.  
  31. if __name__ == "__main__":
  32.     try:
  33.         ciphertext = input().strip()
  34.         known_word = input().strip()
  35.         print(decipher(ciphertext, known_word))
  36.     except EOFError:
  37.         print("levalid")
Success #stdin #stdout 0.07s 14116KB
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levalid
https://ideone.com/Kckgtu
language:
Python 3 (python  3.12)
created:
4 days ago
visibility:
public

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