Thaithanhhai202400085

exercise/ps4b.py

@@ -18,13 +18,17 @@ def load_words(file_name):
     '''
     print("Loading word list from file...")
     # inFile: file
-    inFile = open(file_name, 'r')
-    # wordlist: list of strings
-    wordlist = []
-    for line in inFile:
-        wordlist.extend([word.lower() for word in line.split(' ')])
-    print("  ", len(wordlist), "words loaded.")
-    return wordlist
+    try:
+        inFile = open(file_name, 'r')
+        # wordlist: list of strings
+        wordlist = []
+        for line in inFile:
+            wordlist.extend([word.lower() for word in line.split(' ')])
+        print("  ", len(wordlist), "words loaded.")
+        return wordlist
+    except FileNotFoundError:
+        print(f"Warning: File {file_name} not found!")
+        return []
 
 def is_word(word_list, word):
     '''
@@ -35,12 +39,6 @@ def is_word(word_list, word):
     word (string): a possible word.
 
     Returns: True if word is in word_list, False otherwise
-
-    Example:
-    >>> is_word(word_list, 'bat') returns
-    True
-    >>> is_word(word_list, 'asdf') returns
-    False
     '''
     word = word.lower()
     word = word.strip(" !@#$%^&*()-_+={}[]|\:;'<>?,./\"")
@@ -50,10 +48,14 @@ def get_story_string():
     """
     Returns: a story in encrypted text.
     """
-    f = open("story.txt", "r")
-    story = str(f.read())
-    f.close()
-    return story
+    try:
+        f = open("story.txt", "r")
+        story = str(f.read())
+        f.close()
+        return story
+    except FileNotFoundError:
+        print("Warning: story.txt not found!")
+        return ""
 
 ### END HELPER CODE ###
 
@@ -70,15 +72,16 @@ def __init__(self, text):
             self.message_text (string, determined by input text)
             self.valid_words (list, determined using helper function load_words)
         '''
-        pass #delete this line and replace with your code here
+        self.message_text = text
+        self.valid_words = load_words(WORDLIST_FILENAME)
 
     def get_message_text(self):
         '''
         Used to safely access self.message_text outside of the class
 
         Returns: self.message_text
         '''
-        pass #delete this line and replace with your code here
+        return self.message_text
 
     def get_valid_words(self):
         '''
@@ -87,7 +90,7 @@ def get_valid_words(self):
 
         Returns: a COPY of self.valid_words
         '''
-        pass #delete this line and replace with your code here
+        return self.valid_words[:]
 
     def build_shift_dict(self, shift):
         '''
@@ -103,7 +106,17 @@ def build_shift_dict(self, shift):
         Returns: a dictionary mapping a letter (string) to 
                  another letter (string). 
         '''
-        pass #delete this line and replace with your code here
+        lower_keys = string.ascii_lowercase
+        upper_keys = string.ascii_uppercase
+        shift_dict = {}
+
+        for i in range(26):
+            # Map lowercase
+            shift_dict[lower_keys[i]] = lower_keys[(i + shift) % 26]
+            # Map uppercase
+            shift_dict[upper_keys[i]] = upper_keys[(i + shift) % 26]
+
+        return shift_dict
 
     def apply_shift(self, shift):
         '''
@@ -117,7 +130,14 @@ def apply_shift(self, shift):
         Returns: the message text (string) in which every character is shifted
              down the alphabet by the input shift
         '''
-        pass #delete this line and replace with your code here
+        mapping_dict = self.build_shift_dict(shift)
+        encrypted_text = []
+        for char in self.message_text:
+            if char in mapping_dict:
+                encrypted_text.append(mapping_dict[char])
+            else:
+                encrypted_text.append(char)
+        return "".join(encrypted_text)
 
 class PlaintextMessage(Message):
     def __init__(self, text, shift):
@@ -135,31 +155,34 @@ def __init__(self, text, shift):
             self.message_text_encrypted (string, created using shift)
 
         '''
-        pass #delete this line and replace with your code here
+        Message.__init__(self, text)
+        self.shift = shift
+        self.encryption_dict = self.build_shift_dict(shift)
+        self.message_text_encrypted = self.apply_shift(shift)
 
     def get_shift(self):
         '''
         Used to safely access self.shift outside of the class
 
         Returns: self.shift
         '''
-        pass #delete this line and replace with your code here
+        return self.shift
 
     def get_encryption_dict(self):
         '''
         Used to safely access a copy self.encryption_dict outside of the class
 
         Returns: a COPY of self.encryption_dict
         '''
-        pass #delete this line and replace with your code here
+        return self.encryption_dict.copy()
 
     def get_message_text_encrypted(self):
         '''
         Used to safely access self.message_text_encrypted outside of the class
 
         Returns: self.message_text_encrypted
         '''
-        pass #delete this line and replace with your code here
+        return self.message_text_encrypted
 
     def change_shift(self, shift):
         '''
@@ -171,7 +194,9 @@ def change_shift(self, shift):
 
         Returns: nothing
         '''
-        pass #delete this line and replace with your code here
+        self.shift = shift
+        self.encryption_dict = self.build_shift_dict(shift)
+        self.message_text_encrypted = self.apply_shift(shift)
 
 
 class CiphertextMessage(Message):
@@ -185,7 +210,8 @@ def __init__(self, text):
             self.message_text (string, determined by input text)
             self.valid_words (list, determined using helper function load_words)
         '''
-        pass #delete this line and replace with your code here
+        # --- ĐÃ SỬA LỖI TẠI DÒNG DƯỚI ĐÂY ---
+        Message.__init__(self, text) 
 
     def decrypt_message(self):
         '''
@@ -196,29 +222,85 @@ def decrypt_message(self):
         the message, then we would expect 26 - s to be the best shift value 
         for decrypting it.
 
-        Note: if multiple shifts are equally good such that they all create 
-        the maximum number of valid words, you may choose any of those shifts 
-        (and their corresponding decrypted messages) to return
-
         Returns: a tuple of the best shift value used to decrypt the message
         and the decrypted message text using that shift value
         '''
-        pass #delete this line and replace with your code here
+        best_shift = 0
+        max_valid_words = 0
+        best_message = ""
+
+        # Try all possible shifts from 0 to 25
+        for s in range(26):
+            # Apply shift to the current ciphertext
+            decrypted_try = self.apply_shift(s)
+
+            # Split into words to check validity
+            words = decrypted_try.split(' ')
+            valid_count = 0
+
+            # Count valid words
+            for word in words:
+                if is_word(self.valid_words, word):
+                    valid_count += 1
+
+            # Update best shift if we found more valid words
+            if valid_count > max_valid_words:
+                max_valid_words = valid_count
+                best_shift = s
+                best_message = decrypted_try
+
+        return (best_shift, best_message)
 
 if __name__ == '__main__':
 
-#    #Example test case (PlaintextMessage)
-#    plaintext = PlaintextMessage('hello', 2)
-#    print('Expected Output: jgnnq')
-#    print('Actual Output:', plaintext.get_message_text_encrypted())
-#
-#    #Example test case (CiphertextMessage)
-#    ciphertext = CiphertextMessage('jgnnq')
-#    print('Expected Output:', (24, 'hello'))
-#    print('Actual Output:', ciphertext.decrypt_message())
+    # Example test case (PlaintextMessage)
+    plaintext = PlaintextMessage('hello', 2)
+    print('Expected Output: jgnnq')
+    print('Actual Output:', plaintext.get_message_text_encrypted())
 
-    #TODO: WRITE YOUR TEST CASES HERE
+    # Example test case (CiphertextMessage)
+    ciphertext = CiphertextMessage('jgnnq')
+    print('Expected Output:', (24, 'hello'))
+    print('Actual Output:', ciphertext.decrypt_message())
 
-    #TODO: best shift value and unencrypted story 
+    # TODO: WRITE YOUR TEST CASES HERE
+    print("\n------------------------------")
+    print("MY CUSTOM TEST CASES:")
+
+    # 1. Test PlaintextMessage
+    print("\n1. Testing PlaintextMessage:")
+    my_msg = PlaintextMessage("Python is awesome!", 4)
+    print("Original:", my_msg.get_message_text())
+    print("Shift:", my_msg.get_shift())
+    print("Encrypted:", my_msg.get_message_text_encrypted())
+
+    # Thay đổi shift
+    print("-> Changing shift to 1...")
+    my_msg.change_shift(1)
+    print("New Encrypted:", my_msg.get_message_text_encrypted())
+
+    # 2. Test CiphertextMessage
+    print("\n2. Testing CiphertextMessage:")
+    # Giả sử ta có chuỗi đã mã hóa: "Python is awesome!" -> shift 1 -> "Qzuipo jt bxftpnf!"
+    encrypted_str = "Qzuipo jt bxftpnf!" 
+    cipher_msg = CiphertextMessage(encrypted_str)
+
+    # Giải mã
+    result = cipher_msg.decrypt_message()
+    print(f"Input Encrypted: {encrypted_str}")
+    print(f"Best Shift found: {result[0]}")
+    print(f"Decrypted Text: {result[1]}")
+
+    # TODO: best shift value and unencrypted story 
+    print("\n------------------------------")
+    print("DECODING STORY.TXT:")
 
-    pass #delete this line and replace with your code here
+    story_text = get_story_string()
+    if story_text:
+        story_cipher = CiphertextMessage(story_text)
+        decoded_story = story_cipher.decrypt_message()
+        print(f"Best Shift: {decoded_story[0]}")
+        print("Story Content:\n")
+        print(decoded_story[1])
+    else:
+        print("Could not load story.txt to decrypt.")