2020 CCPC Online Contest

Problem A

Unsolved.

Problem B

Solved by all. 02:24:09(+1)

每个节点向其某个质因子连边，之后所有素数向 $2$ 连边。答案即为区间自然数和加上区间素数和，用 min25 筛出即可。

Problem C

Solved by bingoier. 00:27:30

Problem E

Solved by yanghong. 00:36:01(+2)

Problem F

Solved by Once. 04:43:11(+4)

把所有边界点带入后方的连续函数验证连续性即可。

取消同步要人命。

Problem G

Solved by Once. 00:16:43

大胆猜测答案就是出现最多的字母的出现次数。

Problem J

Solved by Once. 00:08:01

检查是否有相邻的 $1$ 即可。

Problem K

Solved by Once. 00:45:19(-1)

大胆猜测，当且仅当只有左上角非零时答案为原矩阵，感觉证明也挺简单的。