Algorithm/3203.txt at master · Tachone/Algorithm · GitHub

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#include<iostream>
#include<cmath>
#include<iomanip>
using namespace std;
double H,D,h;//放到上面，这样调用函数形参只剩一个
int main()
{
	double f(double x);
	double g(double x);
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>H>>h>>D;
		if(D*(D+h-H)<=0)
		cout<<setiosflags(ios::fixed)<<setprecision(3)<<f(0)<<endl;
		else
		{
		    double st=0,ed=D*h/H,mid=(st+ed)/2;//注意如果墙上没有影子后，那么在
			while (ed-st>1e-9)//转弯处是最大值，所以注意二分的取值范围
			{

			    if(g(mid)<0)
				ed=mid;
				else
				st=mid;
				mid=(ed+st)/2;
			}
			cout<<setiosflags(ios::fixed)<<setprecision(3)<<f(mid)<<endl;
		}
	}
	return 0;
}
double f(double x)
{
	return (D*x-x*x+D*h-x*H)/(D-x);
}
double g(double x)
{
	return (x*x-2*D*x+D*D+D*h-H*D)/(D-x)*(D-x);
}


#include<iostream>
#include<iomanip>
using namespace std;
double h,H,D;
int main()
{
	double f(double x);
	int n;
	cin>>n;
	for(int i=1;i<=n;i++)
	{
		cin>>H>>h>>D;
		if(D*(D+h-H)<=0)
		cout<<setiosflags(ios::fixed)<<setprecision(3)<<f(0)<<endl;
		else
		{
			double st=0,ed=D*h/H;
			double mid=(st+ed)/2;
			double midmid = (mid+ed)/2;
			while(midmid-mid>1e-8)
			{
				if(f(midmid)>f(mid))
				st=mid;
				else
				ed=midmid;
				mid=(st+ed)/2;
				midmid = (mid+ed)/2;
			}
			cout<<setiosflags(ios::fixed)<<setprecision(3)<<f(mid)<<endl;

		}
	}

	return 0;
}
double f(double x)
{
	return (D*x-x*x+D*h-x*H)/(D-x);
}