给定指定顺序，获取列中所有重复元素的索引

def get_duplicate_indices(lst):
    indices_dict = {}
    for i, element in enumerate(lst):
        if element in indices_dict:
            indices_dict[element].append(i)
        else:
            indices_dict[element] = [i]

    duplicate_indices = []
    for element, indices in indices_dict.items():
        if len(indices) > 1:
            duplicate_indices.extend(indices)

    return duplicate_indices

lst = [1, 2, 3, 4, 3, 2, 1]
result = get_duplicate_indices(lst)
print(result)  # 输出：[2, 4, 5]