Submission #638428

#	Time	Username	Problem	Language	Result	Execution time	Memory
638428		LeticiaFCS	Mobile (BOI12_mobile)	C++17	0 / 100	1092 ms	98492 KiB

mobile

#include "bits/stdc++.h"
#define st first
#define nd second
using lint = int64_t;
constexpr int MOD = int(1e9) + 7;
constexpr int INF = 0x3f3f3f3f;
constexpr int NINF = 0xcfcfcfcf;
constexpr lint LINF = 0x3f3f3f3f3f3f3f3f;
const long double PI = acosl(-1.0);
// Returns -1 if a < b, 0 if a = b and 1 if a > b.
int cmp_double(double a, double b = 0, double eps = 1e-9) {
	return a + eps > b ? b + eps > a ? 0 : 1 : -1;
}
using namespace std;

using ld = long double;

int main() {
	cin.tie(nullptr)->sync_with_stdio(false);
	int n;
	lint length;
	cin>>n>>length;
	vector<lint> x(n), y(n);
	for(int i=0; i<n; i++)
		cin>>x[i]>>y[i];
	
	ld l = 0, r = length;
	int it = 300;
	while(it--){
		ld mid = (l+r)/2;
		vector<pair<ld, bool>> intervals;
		for(int i=0; i<n; i++){
			ld xaux = sqrtl(mid*mid - y[i]*y[i]);
			intervals.push_back({max(ld(0), x[i] - xaux), 0});
			intervals.push_back({min(ld(length), x[i] + xaux), 1});
		}
		bool possible = true;
		sort(intervals.begin(), intervals.end());
		intervals.push_back({length, 0});
		ld last = 0;
		int open = 0;
		for(auto &[position, type]:intervals){
			if(type == 0){
				if(open == 0 && cmp_double(last, position) == -1){
					possible = false;
				}
				open++;
			} else open--;
			last = position;
		}
		
		if(possible) r = mid;
		else l = mid;
	}
	cout<<fixed<<setprecision(5)<<r<<"\n";
	

	return 0;
}
/*
[  ]Leu o problema certo???
[  ]Ver se precisa de long long
[  ]Viu o limite dos fors (é n? é m?)
[  ]Tamanho do vetor, será que é 2e5 em vez de 1e5??
[  ]Testar sample
[  ]Testar casos de  borda
[  ]1LL no 1LL << i
[  ]Testar mod (é 1e9+7, mesmo?, será que o mod não ficou negativo?)
*/

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