Submission #126735

#	Time	Username	Problem	Language	Result	Execution time	Memory
126735		Mahmoud_Adel	Mobile (BOI12_mobile)	C++14	0 / 100	1077 ms	39280 KiB

mobile

#include <bits/stdc++.h>
using namespace std;
#define f first
#define s second
typedef long long ll;
const int N = 1e6+5, mod = 1e9+7;
int n, m;
pair<double, double> p[N];
stack<pair<int, pair<double, double>>> s;
double dis(int i, double x)
{
	double y = 0;
	return hypot((x-p[i].f), (y-p[i].s));
}
int main()
{
	cin >> n >> m;
	for(int i=0; i<n; i++) cin >> p[i].f >> p[i].s;
	for(int i=0; i<n; i++)
	{
		if(s.empty()) s.push({i, {0, m}});
		else
		{
			auto t = s.top();
			if(dis(t.f, t.s.f) >= dis(i, t.s.f))
			{
				s.pop();
				s.push({i, {t.s.f, t.s.s}});
			}
			else if(dis(t.f, t.s.s) > dis(i, t.s.s))
			{
				double x, x1 = p[i].f, x2 = p[t.f].f;
				double y1 = p[i].s, y2 = p[t.f].s;
				x = (x1*x1 - x2*x2 + y1*y1-y2*y2)/(2*x1-2*x2);
				s.pop();
				t.s.s = x;
				s.push(t), s.push({i, {x, m}});
			}
		}
	}
	double ans = 0;
	while(!s.empty())
	{
		auto t = s.top();
		s.pop();
		ans = max(ans, max(dis(t.f, t.s.f), dis(t.f, t.s.s)));
	}
	cout << fixed << setprecision(4) << ans << endl;
}

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