加密算法实例：替换密码

def simple_sub_cipher(text, substitution_map):
    encrypted_text = []
    plaintext_length = len(text)
    
    for i in range(plaintext_length):
        if text[i] in substitution_map:
            encrypted_text.append(substitution_map[text[i]])
        else:
            encrypted_text.append(text[i])
    return ''.join(encrypted_text)

def main():
    plain_text = 'Hello, World!'
    cipher_text = simple_sub_cipher(plain_text, substitution_map)
    
    print("Plaintext:", plain_text)
    print("Ciphertext:", cipher_text)
    decrypted_text = simple_sub_cipher(cipher_text, substitution_map)
    print("Decrypted Plaintext:", decrypted_text)

# 加密映射
substitution_map = {
    'A': 'Z',
    'B': 'Y',
    'C': 'X',
    'D': 'W',
    'E': 'V',
    'F': 'U',
    'G': 'T',
    'H': 'S',
    'I': 'R',
    'J': 'Q',
    'K': 'P',
    'L': 'O',
    'M': 'N',
    'O': 'M',
    'P': 'L',
    'Q': 'K',
    'R': 'J',
    'S': 'I',
    'T': 'H',
    'U': 'G',
    'V': 'F',
    'W': 'E',
    'X': 'D',  # 需要替换所有非字母字符
    'Y': 'C',
    'Z': 'B'
}

def simple_sub_decipher(ciphertext, substitution_map):
    decrypted_text = []
    ciphertext_length = len(ciphertext)
    
    for i in range(ciphertext_length):
        if ciphertext[i] in substitution_map:
            decrypted_text.append(substitution_map[ciphertext[i]])
        else:
            decrypted_text.append(ciphertext[i])
    return ''.join(decrypted_text)