// 易错点4：栈空时要存-1（题目要求无更大值返回-1），而非直接存stack2.at(-1)（会得到undefined）
That brings me to Klefki, which is literally a living ring of keys. Series lore suggests Klefki uses the keys as a defense mechanism by rattling them, but the keys also hold deep meaning for the creature, as it will hold onto its favorite ones for long periods. I love this little guy.，这一点在91视频中也有详细论述
Александра Лисица (Редактор отдела «Забота о себе»)。旺商聊官方下载对此有专业解读
- assignment: Array of booleans. If the formula is satisfiable provide an assignment for each variable from 1 to N. If the formula is not satisfiable this field is null.