POJ 2976 Dropping tests (0/1分数规划)
Time Limit: 1000MS | Memory Limit: 65536K | |
Total Submissions: 4654 | Accepted: 1587 |
Description
In a certain course, you take n tests. If you get ai out of bi questions correct on test i, your cumulative average is defined to be
.
Given your test scores and a positive integer k, determine how high you can make your cumulative average if you are allowed to drop any k of your test scores.
Suppose you take 3 tests with scores of 5/5, 0/1, and 2/6. Without dropping any tests, your cumulative average is . However, if you drop the third test, your cumulative average becomes .
Input
The input test file will contain multiple test cases, each containing exactly three lines. The first line contains two integers, 1 ≤ n ≤ 1000 and 0 ≤ k < n. The second line contains n integers indicating ai for all i. The third line contains n positive integers indicating bi for all i. It is guaranteed that 0 ≤ ai ≤ bi ≤ 1, 000, 000, 000. The end-of-file is marked by a test case with n = k = 0 and should not be processed.
Output
For each test case, write a single line with the highest cumulative average possible after dropping k of the given test scores. The average should be rounded to the nearest integer.
Sample Input
3 1
5 0 2
5 1 6
4 2
1 2 7 9
5 6 7 9
0 0
Sample Output
83
100
Hint
To avoid ambiguities due to rounding errors, the judge tests have been constructed so that all answers are at least 0.001 away from a decision boundary (i.e., you can assume that the average is never 83.4997).
Source
给定ai和bi,求100*sigma(ai*xi)/sigma(bi*xi)的最大值,xi=0或1,且只能有k个为0。
即可以去掉k个(ai,bi)对。
y=100*sigma(ai)/sigma(bi)
t(y)=100*sigma(ai)-y*sigma(bi)
求t(y0)=0;
当t(y)<0时,y太大,y0<y;
当t(y)>0时,y太小,y<y0;
所以可以二分y的值。
去哪k个更优了?
要使y更大就应该是t(y)>0这种情况更可能的出现,所以对100*ai-bi排序,去掉小的k个。使t(y)>0城里更有可能。
#include<iostream>
#include<cstdio>
#include<cstring>
#include<algorithm>
#include<cmath> using namespace std; const int N=;
const double eps=1e-; int n,k;
double a[N],b[N],score[N]; int main(){ //freopen("input.txt","r",stdin); while(~scanf("%d%d",&n,&k)){
if(n== && k==)
break;
for(int i=;i<n;i++)
scanf("%lf",&a[i]);
for(int i=;i<n;i++)
scanf("%lf",&b[i]);
double l=,r=,mid,sum;
while(r-l>eps){
mid=(l+r)/;
for(int i=;i<n;i++)
score[i]=*a[i]-mid*b[i];
sort(score,score+n);
sum=;
for(int i=k;i<n;i++)
sum+=score[i];
if(sum>)
l=mid;
else
r=mid;
}
printf("%.0f\n",l);
}
return ;
}
最新文章
- core文件
- 纪念逝去的岁月——C++实现一个栈
- 是否采用Sybase形式的自动字符串转义(用 &#39;&#39; 表示 &#39;)
- Ant build ${renderscript.opt.level}问题解决方案
- [JavaScript] 初中级Javascript程序员必修学习目录
- 兔子--R.java丢失原因及解决的方法
- javascript改变背景/字体颜色(Through the javascript to change the background and font color)
- mercurial(Hg) Server 搭建 过程记录
- HeadFirst设计模式读书笔记--目录
- Linux系统服务 1 ---- rSyslog日志服务
- jenkins配置.net mvc网站
- 化繁为简 经典的汉诺塔递归问题 in Java
- 【Sqoop篇】----Sqoop从搭建到应用案例
- FC105 FC106 Scale功能块使用说明
- H5端密码控件自动化测试
- transform 图标旋转,IE8、IE7不兼容
- Netty4.x 源码实战系列(一): 深入理解ServerBootstrap 与 Bootstrap
- flume杀掉重启
- 布式实时日志系统(三) 环境搭建之centos 6.4下hadoop 2.5.2完全分布式集群搭建最全资料
- c# 修改pdf
热门文章
- BigDecimal 的幂次方运算
- 结构体指针之 段错误 具体解释(segmentation fault)
- Android 自定义 ListView 上下拉动刷新最新和加载更多
- jquery 文字滚动大全 scroll 支持文字或图片 单行滚动 多行滚动 带按钮控制滚动
- javascript string replace 正则替换
- JavaScript的valueOf和toString
- SpringMVC+SPring+Maven+Mybaits+Shiro+Mybaits基础开发项目
- 朴素贝叶斯分类器(Naive Bayes)
- ES6学习笔记八:类与继承
- 【转发】JQuery中操作Css样式的方法