开始要把所有入度为 $0$ 的点都 $\texttt{push}$ 进去。
by aCssen @ 2022-11-24 12:26:02
@[aCssen](/user/534296) 我也是上面的情况，A了，Thank you！
by K__J__M @ 2023-08-09 09:17:50
@[aCssen](/user/534296) 感谢！
by JiuZhE66666 @ 2023-12-26 17:18:13