从较大的字符串中删除字符并重新添加字符，但确保不使用相同的无效字符

def remove_and_add_characters(string, characters_to_remove, characters_to_add):
    # 删除字符
    for char in characters_to_remove:
        string = string.replace(char, '')

    # 添加字符
    for char in characters_to_add:
        # 根据需要插入字符的位置，可以使用不同的插入方法
        # 这里使用了简单的在字符串末尾添加字符的方法
        string += char

    return string

# 示例用法
original_string = "This is a sample string."
characters_to_remove = ['a', 's']
characters_to_add = ['x', 'y', 'z']

new_string = remove_and_add_characters(original_string, characters_to_remove, characters_to_add)
print(new_string)