2018 Multi-University, Nowcoder Day 8

Problem B

Solved by OEIS. 01:12 (+)

Brute force by ultmaster.

题意：染棋盘上不同行不同列的 $n$ 个格子，使得经过一系列两个相邻格子都染黑则染黑的操作之后，所有格子都能染黑。

题解：$a_n = \frac{1}{n} \sum_{k=0}^n 2^k \binom{n}{k} \binom{n}{k-1}$。

Problem E

Solved by ultmaster. 03:12 (+)

Problem G

Solved by kblack. 00:13 (+)

Problem H

Solved by zerol & ultmaster. 02:47 (+6)