Difference between revisions of "2018 Multi-University, HDU Day 3"

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Solved by ultmaster. 02:27 (+)
 
Solved by ultmaster. 02:27 (+)
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题意:给一些点,让你选其中一些点,从左到右,然后和 $(0,0)$ 组成一把扇子,使得扇子的有向面积最大。
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 +
题解:其实就是求一个上凸壳。魔改凸包的单调栈即可。注意本题要求输出字典序最小,还会有重点。不过都是小问题,稍微注意一点不会写错。
  
 
== Problem I ==
 
== Problem I ==

Revision as of 12:39, 30 July 2018

Problem A

Solved by kblack. 01:45 (+5)

Problem C

Solved by ultmaster. 00:53 (+)

题意:若干加边删边操作,每次操作后,询问图中 $1,2,\ldots,n/2$ 匹配的数目。

题解:由于 $n$ 很小,维护每一个子图 ($2^n$) 的匹配数目。加边的时候,把含有那条边的子图都加上去掉那条边的子图的部分的现有的值。删边同理。

ultmaster: 总觉得有什么地方不大对,但出乎意料地输出了正确的答案。(运气真好)

Problem D

Solved by ultmaster. 00:17 (+)

题意:求第 $k$ 个欧拉函数是合数的数。

题解:经典的打表找规律签到。

Problem F

Solved by zerol. 00:26 (+)

Problem G

Solved by ultmaster. 02:27 (+)

题意:给一些点,让你选其中一些点,从左到右,然后和 $(0,0)$ 组成一把扇子,使得扇子的有向面积最大。

题解:其实就是求一个上凸壳。魔改凸包的单调栈即可。注意本题要求输出字典序最小,还会有重点。不过都是小问题,稍微注意一点不会写错。

Problem I

Solved by kblack. 03:24 (+4)

Problem J

Unsolved. (-2)

Problem L

Solved by kblack. 00:22 (+)

Problem M

Solved by zerol. 03:40 (+)