soj 1698 Hungry Cow_三角函数

来源：互联网发布：路边停车收费软件编辑：程序博客网时间：2024/05/17 04:53

题目链接

题意：有只牛要吃草，现在有个墙挡着，给你绑着牛的绳的长度，墙的长度，绳原点到墙的距离，问牛能在多大的面积里吃草

思路：分为四种情况，详情请看书。被dp卡着这题没做成

#include <iostream>#include<cstdio>#include<cmath>#include<cstring>using namespace std;#define eps 1e-8const double PI=acos(-1.0);double l,d,s;double solve(){if(s-d<eps)//1 return PI*s*s;double dist=sqrt(0.25*l*l+d*d),ans=0;if(s-dist<eps){//2double angle=acos(d/s);ans=(PI-angle)*s*s+s*d*sin(angle);}else{//3,4double angle=asin(0.5*l/dist);ans+=(PI-angle)*s*s+0.5*l*d;s-=dist;angle+=0.5*PI;ans+=angle*s*s;if(s+s-l>eps){double angle1=acos(0.5*l/s);ans-=angle1*s*s-0.5*sin(angle1)*s*l;}}return ans;}int main(int argc, char** argv) {int t;double ans;scanf("%d",&t);while(t--){scanf("%lf%lf%lf",&l,&d,&s);ans=solve();printf("%.2lf\n",ans);}return 0;}

0 0