Submission #654945

#	Time	Username	Problem	Language	Result	Execution time	Memory
654945		Koful123	Mobile (BOI12_mobile)	C++17	0 / 100	1097 ms	15956 KiB

mobile

#include <bits/stdc++.h>
using namespace std;
#define int long long
//#define endl "\n"
#define pb push_back
#define ff first
#define ss second
#define mod 1000000007
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()

const double eps = 0.0000000000000001;

double dis(pair<double,double> x,pair<double,double> y){
	return sqrt(pow(x.ff - y.ff,2) + pow(x.ss - y.ss,2));
}

void solve(){

	double n,k;
	cin >> n >> k;

	vector<pair<double,double>> v(n);
	for(auto &[x,y] : v){
		cin >> x >> y;
	}

	auto check = [&](double m,int i,int ty){
		double d = 1e18,e = 1e18;
		for(int j=0;j<i;j++){
			d = min(d,dis({m,0},v[j]));
		}
		for(int j=i;j<n;j++){
			e = min(e,dis({m,0},v[j]));	
		}
		if(ty == 3) return d;
		if(ty == 2) return double(d <= e);
		if(ty == 1) return double(d <= e);
		return double(d >= e);
	};

	double ans = 0;
	for(int i=1;i<n;i++){
		double l = 0,r = k;
		int ty = check(v[i-1].ff,i,2);
		for(int j=1;j<=66;j++){
			double m = (l + r + eps) / 2;
			if(check(m,i,ty)) l = m;
			else r = m - eps;
		}
		ans = max(ans,check(l,i,3));
	}

	cout << fixed << setprecision(10);
	cout << ans << endl;
}	

signed main(){

	ios::sync_with_stdio(0);
	cin.tie(0);

	int t = 1;
//	cin >> t;

	while(t--)
		solve();

	return 0;
}

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