Submission #919366

#	Time	Username	Problem	Language	Result	Execution time	Memory
919366		ethanv13	Mobile (BOI12_mobile)	C++17	0 / 100	1055 ms	66124 KiB

mobile

#include <bits/stdc++.h>
using namespace std;
vector<pair<long long,long long>>c;long long n,l;
bool can(long double mid){
	vector<pair<long double,long double>>seg;
	for(int i=0;i<n;++i){
		if(mid<abs(c[i].second)){
			return false;
		}
		else {
			long double delta=sqrt(mid*mid-c[i].second*c[i].second);
			seg.push_back({c[i].first-delta,c[i].first+delta});
		}
	}
	long double minx=4e9;
	long double currub=-4e9;
	for(int i=0;i<n;++i){
		if(minx>seg[i].first){
			minx=seg[i].first;
		}
		if(seg[i].first<=currub||currub==-4e9){
			currub=seg[i].second;continue;
		}
		else {
			return false;
		}
	}
	return currub>=l&&minx<=0;
}
int main() {
	cin>>n>>l;
	for(int i=0;i<n;++i){
		long long x,y;cin>>x>>y;c.push_back({x,y});
	}
	long double lo=0;long double hi=2e9;
	for(int i=0;i<50;++i){
		long double mid=(lo+hi)/2;
		if(can(mid)){
			hi=mid;
		}
		else {
			lo=mid;
		}
	}
	cout<<fixed<<setprecision(9);
	cout<<lo<<endl;
};

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