Submission #1167878

#	Time	Username	Problem	Language	Result	Execution time	Memory
1167878		julia_08	Mobile (BOI12_mobile)	C++20	0 / 100	1096 ms	65340 KiB

mobile

#include <bits/stdc++.h>
using namespace std;

using ld = long double;
using ll = long long;

const int MAXN = 1e6 + 10;

ll x[MAXN], y[MAXN];

int n; ll L;

bool check(ld d){

  vector<pair<ld, ld>> segs;

  for(int i=1; i<=n; i++){

    ld delta = (ld) (d * d - y[i] * y[i]);

    if(delta < 0.000) continue;

    ld l = (ld) (x[i] - sqrt(delta)), r = (ld) (x[i] + sqrt(delta));

    if(r >= 0.000) segs.push_back({max(l, (ld) 0.000), r});

  }

  if(segs.empty()) return true;

  sort(segs.begin(), segs.end());

  if(segs[0].first > 0.000 || segs[(int) segs.size() - 1].second < L) return true;

  for(int i=1; i<(int) segs.size(); i++){
    if(segs[i].first - segs[i - 1].second > 0.000){
      return true;
    }
  }

  return false;
}

ld bs(){

  ld l = 0, r = 1e10;

  for(int i=0; i<75; i++){
    ld m = (l + r) / 2;
    if(check(m)) l = m;
    else r = m;
  }

  return l;
}

int main(){
  cin.tie(0)->sync_with_stdio(0);

  cin >> n >> L;

  for(int i=1; i<=n; i++){
    cin >> x[i] >> y[i];
  }

  cout << fixed << setprecision(6) << bs() << "\n";

  return 0;
}

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