VK Cup 2017 Round 3 + Codeforces Round #412

Posted 2020-09-20 翠竹叶飞

A 读题题

B 就是你排名第p，得了x分，而最终至少需要y分，你需要最少的successful hack，使得最终得分s>=y，且由s随机取25个数，使p被选中。

（1）暴力枚举hack成功几次，失败几次就好了

（2）另解：枚举尽可能小的s，使|s-x|=0(mod 50),分类讨论

If s?≤?x, we need 0 successful hacks, since we can just make (x?-?s)?/?50 unsuccessful hacks.

If s?>?x and s?-?x is divisible by 100, we need exactly (s?-?x)?/?100 successful hacks.

If s?>?x and s?-?x is not divisible by 100, we need (s?-?x?+?50)?/?100 successful hacks and one unsuccessful hack.

 

C 一看到题就打了exgcd，调了一晚上，各种看错，最后发现爆long long了。。

其实列个不等式解就好了