제출 #286487

#	제출 시각	아이디	문제	언어	결과	실행 시간	메모리
286487		__SIGSEGV__	Mobile (BOI12_mobile)	C++17	0 / 100	1094 ms	33380 KiB

mobile

/**
 *    AUTHOR:    __SIGSEGV__                  
 *   CREATED:   30.08.2020 02:54:38  
**/

#include <bits/stdc++.h>

using namespace std;

const double eps = 1e-9;
const double inf = 1e18;

int main(void) {
  ios_base::sync_with_stdio(false);
  cin.tie(0);
  int n;
  double l;
  cin >> n >> l;
  vector<pair<int, int>> points(n);
  for (int i = 0; i < n; i++) {
    cin >> points[i].first >> points[i].second;
    points[i].second = abs(points[i].second);
  }
  sort(points.begin(), points.end());
  vector<pair<double, double>> poi;
  int last;
  for (int i = 0; i < n; i++) {
    poi.emplace_back((double) points[i].first, (double) points[i].second);
    last = points[i].first;
    i++;
    while (i < n && points[i].first == last) ++i;
    --i;
  }
  auto f = [&](double x) {
    double ret = inf;
    for (int i = 0; i < n; i++) {
      double d = sqrt(poi[i].second * poi[i].second + abs(x - poi[i].first) * abs(x - poi[i].first));
      ret = min(ret, d);
    }
    return ret;
  };
  double left = 0, right = l;
  while (abs(right - left) > eps) {
    double x1 = left + (right - left) / 3.0;
    double x2 = right - (right - left) / 3.0;
    double f1 = f(x1), f2 = f(x2);
    cerr << x1 << " " << x2 << '\n';
    if (f1 < f2) left = x1;
    else right = x2;
  }
  double ans = f(left);
  cout.precision(6);
  cout << fixed;
  cout << ans << '\n';
  return 0;
}

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