ACM-ICPC 2018 Jiaozuo Online Contest

ECNU Foreigners

Problem A

Solved by zerol. 00:07 (+)

温暖的签到。

Problem B

Solved by ultmaster. 01:03 (+)

题意：要求从 $n$ 个数中挑出 $m$ 个数，然后用加减乘除等规定的运算符号依次作用在当前的这个数上，结果尽可能大。

题解：最小可能不一定，但最大应该就是维护一个最大一个最小就好了。DP。

Problem E

Solved by kblack. 02:02 (+1)

Problem F

Solved by zerol. 04:25 (+)

Problem G

Solved by zerol. 00:25 (+)

题意：略

题解：$2^{n-1}$

Problem H

Solved by zerol. 03:26 (+2)

Problem I

Solved by zerol. 00:15 (+)

Problem J

Solved by ultmaster. 02:27 (+1)

题意：问一个数是否是完全平方数，问 $1+2+\cdots+k$ 是否是完全平方数。

题解：二分，大数。有点卡常，后面一问优化了常数才过。

另解：模质数做二次剩余，但是被队友拦住了。

Problem K

Solved by kblack. 00:46 (+2)

Problem L

Solved by kblack. 00:19 (+)