zoj 3023 Light Bulb

题目大意:

求L的最大值

思路:

可以想象出是一个关于人到灯泡距离x的单峰上凸函数

当光线在墙角左边的时候影子在不断增长

然后通过相似可以推出人在墙上影子的长度为:H+D*(h-H)/x

再加上地上的D-x就可以计算出每个x的函数值了

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cmath>
 4 #include<cstdlib>
 5 #include<cstring>
 6 #include<algorithm>
 7 #include<vector>
 8 #include<queue>
 9 #define inf 2139062143
10 #define ll long long
11 #define MAXN 1001000
12 #define eps 1e-4
13 using namespace std;
14 inline int read()
15 {
16     int x=0,f=1;char ch=getchar();
17     while(!isdigit(ch)) {if(ch==‘-‘) f=-1;ch=getchar();}
18     while(isdigit(ch)) {x=x*10+ch-‘0‘;ch=getchar();}
19     return x*f;
20 }
21 double H,h,d;
22 double calc(double x){return H+(h*d-H*d)/x+d-x;}
23 int main()
24 {
25     int T=read();
26     while(T--)
27     {
28         scanf("%lf%lf%lf",&H,&h,&d);
29         double r=d,l=d-h*d/H,ml,mr;
30         while(r-l>eps)
31         {
32             ml=(r-l)/3.0+l,mr=2*(r-l)/3.0+l;
33             if(calc(ml)>calc(mr)) r=mr;
34             else l=ml;
35         }
36         printf("%.3lf\n",calc(r));
37     }
38 }

原文地址:https://www.cnblogs.com/yyc-jack-0920/p/9246786.html

时间: 2024-10-18 19:35:55

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