Submission #494119

#	Time	Username	Problem	Language	Result	Execution time	Memory
494119		PikaQ	Mobile (BOI12_mobile)	C++17	0 / 100	4 ms	384 KiB

mobile

#include<bits/stdc++.h>
#define int ll
#define forn(i,n) for(int i=0;i<(n);i++)
#define Forn(i,n) for(int i=1;i<=(n);i++)
#define ll long long
#define pb push_back
#define F first
#define S second
#define lb lower_bound
#define ub upper_bound
#define vi vector<int>
#define vl vector<long long>
#define vpi vector<pair<int,int> >
#define pii pair<int,int>
#define pll pair<long long,long long>
#define mp make_pair
#define rz resize
#define all(p) p.begin(),p.end()
#define alr(p,q) p+1,p+q+1
#define ull unsigned long long
#define st0(p) memset((p),0,sizeof(p))
#define T(x) ((x)%2 ? s[(x)/2] : '.')
#define lowb(x) x&-x
#define ls(x) (x)*2
#define rs(x) (x)*2+1
using namespace std;

inline void USACO(string filename){
	freopen((filename+".in").c_str(),"r",stdin);
	freopen((filename+".out").c_str(),"w",stdout);
}

void debug() {cout << endl;}
template <class T, class ...U> void debug(T a, U ... b) { cout << a << " "; debug(b...);}
// template <class T> int max(T a, T ... b) { cout << a << " "; debug(b...);}
const int INF = 1e9+7;
const double eps = 1e-7;
const int N = 8e2+9;
int n;
double L;
#define pdd pair<double,double> 
vector<pdd> p;


bool check(double R){
	stack<pdd> sk;
	for(auto &i : p){
		double dy = abs(i.S);
		if(dy > R) continue;
		double d = sqrt(R*R - dy*dy);
		double l = i.F -d,r = i.F +d;
		l = max((double)0,l),r = min(L,r);
		while(!sk.empty() && sk.top().F > l){
			sk.pop();
		}
		sk.push({l,r});
	}
	stack<pdd> che;
	while(!sk.empty()){
		che.push(sk.top());
		sk.pop();
	}
	// debug(sk.size(),che.size());
	double l = che.top().F,r = che.top().S;
	che.pop();
	while(!che.empty()){
		pdd now = che.top();che.pop();
		// debug(r,now.F);
		if(now.F > r) return 0;
		r = max(r,now.S);
	}
	// debug(l,r);
	return (l == 0 && r == L);
}

void solve(){
	cin >> n >> L;
	p.rz(n);
	forn(i,n) cin >> p[i].F >> p[i].S;
	sort(all(p));
	double lo = 0,hi = L;
	int cnt = 1e5+1;	
	while(hi - lo > 1e-7){
		double mid = (lo+hi)/2;
		if(check(mid)) hi = mid;
		else lo = mid;
	}
	cout << hi << '\n';
}		 	



signed main(){
	// USACO("angry");
	cin.tie(0);
	cout.tie(0);
	ios_base::sync_with_stdio(0);

	#ifndef ONLINE_JUDGE
		freopen("input.txt", "r", stdin);
		freopen("output.txt", "w", stdout);
	#endif

	// int t;
	// cin >> t;
	// while(t--)
		solve();
	return 0;
}

Compilation message (stderr)

mobile.cpp: In function 'void solve()':
mobile.cpp:82:6: warning: unused variable 'cnt' [-Wunused-variable]
   82 |  int cnt = 1e5+1;
      |      ^~~
mobile.cpp: In function 'int main()':
mobile.cpp:100:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  100 |   freopen("input.txt", "r", stdin);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~
mobile.cpp:101:10: warning: ignoring return value of 'FILE* freopen(const char*, const char*, FILE*)' declared with attribute 'warn_unused_result' [-Wunused-result]
  101 |   freopen("output.txt", "w", stdout);
      |   ~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~

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