【2017 World Final E】Need For Speed(二分)
Sheila is a student and she drives a typical student car: it is old, slow, rusty, and falling apart. Recently, the needle on the speedometer fell off. She glued it back on, but she might have placed it at the wrong angle. Thus, when the speedometer reads v, her true speed is v+c, where c is an unknown constant (possibly negative).
Sheila made a careful record of a recent journey and wants to use this to compute c. The journey consisted of n segments. In the ith segment she traveled a distance of di and the speedometer read vi for the entire segment. This whole journey took time t. Help Sheila by computing c.
Note that while Sheila’s speedometer might have negative readings, her true speed was greater than zero for each segment of the journey.
Input
The first line of input contains two integers n (1≤n≤1000), the number of sections in Sheila’s journey, and t (1≤t≤106), the total time. This is followed by n lines, each describing one segment of Sheila’s journey. The ith of these lines contains two integers di (1≤di≤1000) and v (|vi|≤1000), the distance and speedometer reading for the ith segment of the journey. Time is specified in hours, distance in miles, and speed in miles per hour.
Output
Display the constant c in miles per hour. Your answer should have an absolute or relative error of less than 10−6.
Sample Input 1 | Sample Output 1 |
---|---|
3 5 |
3.000000000 |
Sample Input 2 | Sample Output 2 |
---|---|
4 10 |
-0.508653377 |
题意:
该旅程分为n个部分,每个部分的距离为d[i],速度表所读取的速度为v[i] (v>0),但真实速度为v[i]+c。已知旅程总时间为t,在总误差不超过1e-6的条件下,求c。
思路:
对于方程SUM(d[i]/s[i]+c),利用二分求解的方法求c。
#include<bits/stdc++.h>
#define MAX 1050
using namespace std;
int d[MAX],v[MAX],n;
double t;
int ok(double c)
{
double T=;
for(int i=;i<n;i++)
{
if(c+v[i]<=)return ; //c偏小
else T+=1.0*d[i]/(v[i]*1.0+c);
}
if(T>t)return ;
else return ; //c偏大
}
int main()
{
int i;
while(scanf("%d%lf",&n,&t)!=EOF)
{
for(i=;i<n;i++)
scanf("%d%d",&d[i],&v[i]);
double low=-1e9,high=1e9;
while(high-low>1e-)
{
double mid=(high+low)*0.5;
if(ok(mid))
high=mid;
else low=mid;
}
printf("%.9f\n",(high+low)*0.5);
}
return ;
}
【2017 World Final E】Need For Speed(二分)的更多相关文章
- 8VC Venture Cup 2016 - Final Round D. Preorder Test 二分 树形dp
Preorder Test 题目连接: http://www.codeforces.com/contest/627/problem/D Description For his computer sci ...
- 【bzoj4952】[Wf2017]Need for Speed 二分
题目描述 已知$\sum\limits_{i=1}^n\frac{d_i}{s_i+c}=t$,求$c$ $(d_i>0,s_i+c>0)$ 输入 第一行包含两个整数n(1≤n≤1000) ...
- 2017 world final
E 解题关键:二分时注意C函数的单调性. #include<bits/stdc++.h> #define eps 1e-8 #define INF 0x3f3f3f3f using nam ...
- Intel Code Challenge Final Round D. Dense Subsequence 二分思想
D. Dense Subsequence time limit per test 2 seconds memory limit per test 256 megabytes input standar ...
- World Finals 2017 (水题题解)
看大佬做2017-WF,我这种菜鸡,只能刷刷水题,勉强维持生活. 赛后补补水题. 题目pdf链接,中文的,tls翻译的,链接在这里 个人喜欢在vjudge上面刷题. E Need for Speed ...
- 一个酷炫的,基于HTML5,Jquery和Css的全屏焦点图特效,兼容各种浏览器
基于HTML5和CSS的焦点图特效,梅花图案的背景很有中国特色,而且还会动哦,效果超炫,推荐下载! 演示图 html代码 <!DOCTYPE html PUBLIC "-//W3C// ...
- dedecms织梦建站总结
说好要每月坚持写博客的,差一点就背弃自己的诺言了. 这一个月,除了修改magento站点和学习android外,一心都投在了为一家建筑公司做网站上去了,使用的是dedecms,我主要做的是前端开发,着 ...
- dart基础语法
.关于 runApp() 上面的实例代码中使用了 runApp() 方法,runApp 方法接收的指定参数类型为 Widget,即: runApp(Widget).在 Flutter 的组件树(wid ...
- Spark记录-Scala类和对象
本章将介绍如何在Scala编程中使用类和对象.类是对象的蓝图(或叫模板).定义一个类后,可以使用关键字new来创建一个类的对象. 通过对象可以使用定义的类的所有功能. 下面的图通过一个包含成员变量(n ...
随机推荐
- java基础--提示对话框的使用
java基础--提示对话框的使用 2019-03-17-00:35:50-----云林原创 一.显示信息对话框:使用“JOptionPane.showMessageDialog”显示: 图标 对话 ...
- 个人MySQL股票数据库的建立日记
#!/usr/bin/python# -*- coding: UTF-8 -*- import tushare as tsfrom sqlalchemy import create_engine co ...
- jQuery Custom PopUp Window
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/ ...
- html-框架标签的使用
<frameset> - rows:按照行进行划分 ** <frameset rows="80,*"> - cols:按照列进行划分 ** <fram ...
- 003Angular2中使用ng-bootstrap
1.检查@angular/cli版本 命令行ng -v ,版本号必须大于1.0.0-beta.24 2.新建工程 工程所在目录,命令行ng new my-app --style=scss 带style ...
- sketchup 与 ArcGIS 10 的交互(转)
来自:http://blog.csdn.net/kikitamoon/article/details/9036347 许多用户在 ArcGIS 9.2 时代习惯于使用 Sketchup 插件,但是,9 ...
- mysql 常用操作语句
1 根据表中的其中一个字段的值来修改同行某字段的值 UPDATE radar a INNER JOIN radar b ON a.id=b.id SET a.letter=LEFT(b.filena ...
- Siebel学习笔记
Siebel(escript)的学习:1.Siebel的数据类型 Primitive(原始的)---Number,Integer,Hexadecimal(十六进制),Octal(八进制),Floati ...
- HCNA实验OSPF基础
1.拓扑图 方法: 1.配置接口IP 2.配置OSPF协议: [R2]ospf 100 [R2-ospf-100]area 0 [R2-ospf-100-area-0.0.0.0]network 12 ...
- 再学UML-深入浅出UML类图(一)
在UML 2.0的13种图形中,类图是使用频率最高的UML图之一.Martin Fowler在其著作<UML Distilled: A Brief Guide to the Standard O ...