Submission #374737

#	Time	Username	Problem	Language	Result	Execution time	Memory
374737		wzy	Mobile (BOI12_mobile)	C++11	0 / 100	1086 ms	31340 KiB

mobile

#include <bits/stdc++.h>
using namespace std;
#define F first
#define S second
#define rep(i, a, b) for(int i = a; i < (b); ++i)
#define per(i, a, b) for(int i = b-1; i>=a ; i--)
#define trav(a, x) for(auto& a : x)
#define allin(a , x) for(auto a : x)
#define all(x) begin(x), end(x)
#define sz(x) (int)(x).size()
typedef long long ll;
typedef pair<int, int> pii;
typedef vector<ll> vl;
typedef vector<pii> vpi;
typedef pair<ll,ll> pll;
typedef vector<string> vs;
typedef vector<pll> vpl;
typedef vector<int> vi;
std::mt19937 rng((int) std::chrono::steady_clock::now().time_since_epoch().count());

template <class T> int sgn(T x) { return (x > 0) - (x < 0); }
template<class T>
struct Point {
	typedef Point P;
	T x, y;
	explicit Point(T x=0, T y=0) : x(x), y(y) {}
	bool operator<(P p) const { return tie(x,y) < tie(p.x,p.y); }
	bool operator==(P p) const { return tie(x,y)==tie(p.x,p.y); }
	P operator+(P p) const { return P(x+p.x, y+p.y); }
	P operator-(P p) const { return P(x-p.x, y-p.y); }
	P operator*(T d) const { return P(x*d, y*d); }
	P operator/(T d) const { return P(x/d, y/d); }
	T dot(P p) const { return x*p.x + y*p.y; }
	T cross(P p) const { return x*p.y - y*p.x; }
	T cross(P a, P b) const { return (a-*this).cross(b-*this); }
	T dist2() const { return x*x + y*y; }
	double dist() const { return sqrt((double)dist2()); }
	// angle to x-axis in interval [-pi, pi]
	double angle() const { return atan2(y, x); }
	P unit() const { return *this/dist(); } // makes dist()=1
	P perp() const { return P(-y, x); } // rotates +90 degrees
	P normal() const { return perp().unit(); }
	// returns point rotated 'a' radians ccw around the origin
	P rotate(double a) const {
		return P(x*cos(a)-y*sin(a),x*sin(a)+y*cos(a)); }
	friend ostream& operator<<(ostream& os, P p) {
		return os << "(" << p.x << "," << p.y << ")"; }
};


typedef Point<double> P;
P v[1000005];
int n , L;
double f(double x){
	double ans = 0;

	for(int i = 0 ; i < n; i ++){
		P a(x,0);
		ans = max(ans , (a-v[i]).dist());
	}
	return ans;
}

int32_t main(){
	cin >> n >> L;
	for(int i = 0 ; i < n; i ++)
		cin >> v[i].x >> v[i].y;
	double ans = DBL_MAX;
	double l = 0.00 , r = L;
	while(r-l > 1e-6){
		double m1 = l + (r-l)/3;
		double m2 = r - (r-l)/3;
		if(f(m1) > f(m2)){
			l = m1;
		}
		else{
			r = m2;
		}
	}
	cout << fixed << setprecision(6) << f(l) << endl;
}

Compilation message (stderr)

mobile.cpp: In function 'int32_t main()':
mobile.cpp:68:9: warning: unused variable 'ans' [-Wunused-variable]
   68 |  double ans = DBL_MAX;
      |         ^~~

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