Submission #967267

#	Time	Username	Problem	Language	Result	Execution time	Memory
967267		v_matei	Mobile (BOI12_mobile)	C++17	60 / 100	1043 ms	55284 KiB

mobile

#include <bits/stdc++.h>
#include <cmath>
#include <iomanip>

#define ll long long
#define ull unsigned long long
#define pdd std::pair<double, double>

#define NMAX 1e6
#define LMAX 1e9
#define INF 3e9

struct Tower {
  double x, y;
};
struct Seg {
  double st, fn;
};
double n, l;
std::vector<Tower> s;

void citire() {
  std::cin >> n >> l;
  s.resize(n);
  for (int i = 0; i < n; i++) {
    std::cin >> s[i].x >> s[i].y;
  }
}

double b_search(double lo, double hi, std::function<bool(double)> f) {
  // std::cout << "a\n";
  for (int i = 1; hi - lo > 0.001; i++) {
    double mid = (lo + hi) / 2;
    if (f(mid))
      hi = mid;
    else
      lo = mid;
  }
  return lo;
}

bool find_point(double k) {
  std::vector<Seg> segs;
  for (Tower &it : s) {
    if (k * k < it.y * it.y)
      continue;
    double max_dx = sqrt(k * k - it.y * it.y);
    segs.push_back({it.x - max_dx, it.x + max_dx});
    if (segs.back().st < 0 && segs.back().fn > l)
      return 1;
  }
  double pre = 0;
  for (Seg &it : segs) {
    if (pre >= l)
      return 1;
    if (pre >= it.st)
      pre = std::max(pre, it.fn);
  }
  return pre > l;
}

int main() {
  citire();
  // std::cout << "out\n";
  double k = b_search(0, INF, find_point);
  std::cout << std::setprecision(10) << k;
  return 0;
}

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