Submission #533040

#	Time	Username	Problem	Language	Result	Execution time	Memory
533040		Stormersyle	Mobile (BOI12_mobile)	C++14	0 / 100	1067 ms	56924 KiB

mobile

#include <iostream>
#include <bits/stdc++.h> 
#include <array>
#include <fstream>
#include <string>
#include <algorithm>
#include <cmath>
#include <sstream>  
#include <iomanip>
using namespace std;
using ll=long long;

double N, L;
vector<pair<double, double>> c; //{x, y}

bool check(double R){ //checks to see if max distance >=R is possible; find last true
  vector<pair<double, double>> I;
  for (pair<double, double> coord: c){
    double x=coord.first, y=coord.second;
    I.push_back({x-sqrt(R*R-y*y), x+sqrt(R*R-y*y)});
  }
  sort(I.begin(), I.end());
  // for (auto p: I) cout<<"("<<p.first<<" "<<p.second<<")  ";
  // cout<<"\n";
  int s=0;
  double M=-1000000000; //M=max endpoint so far
  while (I[s].first<0) M=max(M, I[s].second), s++;
  for (int i=s; i<N; i++){ //since I.size()==N
    if (I[i].first>M) return true;
    M=max(M, I[i].second);
  }
  if (L>M) return true;
  return false;
}

int main() {
  cin>>N>>L;
  for (int i=0; i<N; i++){
    double x, y;
    cin>>x>>y;
    c.push_back({x, y});
  }

  ll lo=0, hi=1000000000000000;
	lo--;
	while (lo < hi) {
		ll mid = lo + (hi - lo + 1) / 2;
    double R=mid/1000000.0;
		if (check(R)) {
			lo = mid;
		} else {
			hi = mid - 1;
		}
	}
	cout<<setprecision(6)<<lo/1000000.0;
  // cout<<check(5);
}

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