Submission #115050

#	Time	Username	Problem	Language	Result	Execution time	Memory
115050		luciocf	Mobile (BOI12_mobile)	C++14	4 / 100	1080 ms	848 KiB

mobile

#include <bits/stdc++.h>

#define ff first
#define ss second

using namespace std;

const int maxn = 5e3+10;
const double inf = 1e9+10;

typedef pair<double, double> pt;

int n;
double L;

pt p[maxn];

double dist(pt a, pt b)
{
	double d1 = a.ff-b.ff;
	double d2 = a.ss-b.ss;

	return sqrt(d1*d1 + d2*d2);
}

bool ok(double K)
{
	vector<double> V;

	for (int i = 1; i <= n; i++)
	{
		double x = p[i].ff, y = p[i].ss;

		double delta = sqrt(-y*y + K*K);

		V.push_back(min(L, x+delta)), V.push_back(max(0.00, x-delta));
	}

	double ans = 0.00;

	for (auto x: V)
	{
		double aux = inf;

		for (int i = 1; i <= n; i++)
			aux = min(aux, dist({x, 0.00}, p[i]));

		ans = max(ans, aux);
	}

	return (ans >= K); 
}

double busca(void)
{
	double ini = 0.00, fim = inf, ans = 0.00;

	for (int i = 1; i <= 60; i++)
	{
		double mid = (ini+fim)/2.00;

		if (ok(mid)) ans = mid, ini = mid;
		else fim = mid;
	}

	return ans;
}

int main(void)
{
	scanf("%d %lf\n", &n, &L);

	for (int i = 1; i <= n; i++)
		scanf("%lf %lf", &p[i].ff, &p[i].ss);

	double d1 = inf, d2 = inf;

	for (int i = 1; i <= n; i++)
	{
		d1 = min(d1, dist({0.00, 0.00}, p[i]));

		d2 = min(d2, dist({L, 0.00}, p[i]));
	}

	printf("%.9lf\n", max({d1, d2, busca()}));
}

Compilation message (stderr)

mobile.cpp: In function 'int main()':
mobile.cpp:71:7: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
  scanf("%d %lf\n", &n, &L);
  ~~~~~^~~~~~~~~~~~~~~~~~~~
mobile.cpp:74:8: warning: ignoring return value of 'int scanf(const char*, ...)', declared with attribute warn_unused_result [-Wunused-result]
   scanf("%lf %lf", &p[i].ff, &p[i].ss);
   ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

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