Submission #1322162

#	Time	Username	Problem	Language	Result	Execution time	Memory
1322162		boclobanchat	Mobile (BOI12_mobile)	C++20	0 / 100	232 ms	16076 KiB

mobile

#include<bits/stdc++.h>
using namespace std;
const int MAXN=1e6+5;
long long X[MAXN],Y[MAXN];
double dist(double xa,double ya,double xb,double yb)
{
	return sqrt((xa-xb)*(xa-xb)+(ya-yb)*(ya-yb));
}
double getl(double x,double y,double k)
{
	return x-sqrt(k*k-y*y);
}
double getr(double x,double y,double k)
{
	return x+sqrt(k*k-y*y);
}
int main()
{
	ios::sync_with_stdio(0);
	cin.tie(0);
	cout.tie(0);
	int n,len;
	cin>>n>>len;
	for(int i=1;i<=n;i++) cin>>X[i]>>Y[i];
	double l=0,r=2e9,ans=2e9;
	for(int i=1;i<=n;i++) l=max(l,(double)Y[i]);
	while(r-l>1e-5)
	{
		double mid=(l+r)/2,mx=0;
		for(int i=1;i<=n;i++) if(getl(X[i],Y[i],mid)<=mx) mx=max(mx,getr(X[i],Y[i],mid));
		if(mx>=len) r=ans=mid;
		else l=mid;
	}
	cout<<setprecision(10)<<fixed<<ans;
}

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