제출 #1167861

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
1167861		julia_08	Mobile (BOI12_mobile)	C++20	0 / 100	1097 ms	57480 KiB

mobile

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

using ld = long double;

const int MAXN = 1e6 + 10;

int x[MAXN], y[MAXN];

int n, L;

bool cmp(pair<ld, ld> a, pair<ld, ld> b){
  if(b.first - a.first != 0.000) return b.first - a.first > 0.000;
  return b.second - a.second > 0.000;
}

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) segs.push_back({(ld) (x[i] - sqrt(delta)), (ld) (x[i] + sqrt(delta))});
  }

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

  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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