牛客网暑期ACM多校训练营（第五场）A.gpa 01分数规划

链接：https://www.nowcoder.com/acm/contest/143/A
来源：牛客网
 

时间限制：C/C++ 1秒，其他语言2秒
空间限制：C/C++ 262144K，其他语言524288K
Special Judge, 64bit IO Format: %lld

题目描述

Kanade selected n courses in the university. The academic credit of the i-th course is s[i] and the score of the i-th course is c[i].

At the university where she attended, the final score of her is 

Now she can delete at most k courses and she want to know what the highest final score that can get.

输入描述:

The first line has two positive integers n,k

The second line has n positive integers s[i]

The third line has n positive integers c[i]

输出描述:

Output the highest final score, your answer is correct if and only if the absolute error with the standard answer is no more than 10-5

 

示例1

输入

3 1
1 2 3
3 2 1

输出

2.33333333333

说明

Delete the third course and the final score is 

备注:

1≤ n≤ 105

0≤ k < n

1≤ s[i],c[i] ≤ 10^3 

题目大意：

给出序列s和c，求在最多删除k个课程后最大。

分析：

01分数规划模板题，读者可以参看这篇文章https://blog.csdn.net/hhaile/article/details/8883652

这里直接给出这一题的思路

首先根据01分数规划，我们令，变换后，令

这样只要二分d，对p[i]排序，先取n-k个,剩下的k个只要p[i]<=0时后面的都不需要了（显然是对答案有负贡献的）。

唯一比较麻烦的是精度问题，目测1e-8应该够了（大概）

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