如何根據(jù)字符集和層數(shù)生成不重復(fù)的排列組合，并排除所有字符相同的組合？

def generate_combinations(charset, layers, allow_all_same=False):     results = []     n = len(charset)     all_ones = sum(n**i for i in range(layers))     for i in range(n**layers):         if allow_all_same or i % all_ones != 0:  #排除全同組合             combination = ""             temp = i             for _ in range(layers):                 combination = charset[temp % n] + combination                 temp //= n             results.append(combination)     return results  print(generate_combinations('ab', 2))  # ['ab', 'ba'] print(generate_combinations('ab', 2, True))  # ['aa', 'ab', 'ba', 'bb'] print(generate_combinations('ab', 3))  # ['aab', 'aba', 'abb', 'baa', 'bab', 'bba'] print(generate_combinations('abc', 2))  # ['ab', 'ac', 'ba', 'bc', 'ca', 'cb']

def generate_combinations_recursive(charset, layers, allow_all_same=False):     results = []     current_combination = [''] * layers      def backtrack(index, all_same):         if index == layers:             if not all_same:                 results.append("".join(current_combination))             return         for char in charset:             current_combination[index] = char             backtrack(index + 1, all_same and char == current_combination[index - 1] if index > 0 else False)      for char in charset:         current_combination[0] = char         backtrack(1, not allow_all_same)      return results   print(generate_combinations_recursive('AB', 2))  # ['AB', 'BA'] print(generate_combinations_recursive('AB', 2, True))  # ['AA', 'AB', 'BA', 'BB'] print(generate_combinations_recursive('AB', 3))  # ['AAB', 'ABA', 'ABB', 'BAA', 'BAB', 'BBA'] print(generate_combinations_recursive('ABC', 2))  # ['AB', 'AC', 'BA', 'BC', 'CA', 'CB']