Problem p02764 (C++)

Buggy submission (status: Time Limit Exceeded):
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
// #include<ext/pb_ds/assoc_container.hpp>
// #include<ext/pb_ds/tree_policy.hpp>
// #include<ext/pb_ds/tag_and_trait.hpp>
// using namespace __gnu_pbds;
using namespace std;
using ll = long long;
#define double long double
using datas = pair<ll, ll>;
using ddatas = pair<double, double>;
using tdata = pair<ll, datas>;
using vec = vector<ll>;
using mat = vector<vec>;
using pvec = vector<datas>;
using pmat = vector<pvec>;
// using
// llset=tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>;
#define For(i, a, b) for (i = a; i < (ll)b; i++)
#define bFor(i, a, b) for (i = a; i >= (ll)b; i--)
#define rep(i, N) For(i, 0, N)
#define rep1(i, N) For(i, 1, N)
#define brep(i, N) bFor(i, N - 1, 0)
#define all(v) (v).begin(), (v).end()
#define allr(v) (v).rbegin(), (v).rend()
#define vsort(v) sort(all(v))
#define vrsort(v) sort(allr(v))
#define endl "\n"
#define pb push_back
#define eb emplace_back
#define print(v) cout << v << endl
#define printyes cout << "Yes" << endl
#define printno cout << "No" << endl
#define printYES cout << "YES" << endl
#define printNO cout << "NO" << endl
#define output(v)                                                              \
  do {                                                                         \
    bool f = 0;                                                                \
    for (auto outi : v) {                                                      \
      cout << (f ? " " : "") << outi;                                          \
      f = 1;                                                                   \
    }                                                                          \
    cout << endl;                                                              \
  } while (0)
const ll mod = 1000000007;
const ll inf = 1LL << 60;
const double PI = acos(-1);
const double eps = 1e-9;
template <class T> inline bool chmax(T &a, T b) {
  bool x = a < b;
  if (x)
    a = b;
  return x;
}
template <class T> inline bool chmin(T &a, T b) {
  bool x = a > b;
  if (x)
    a = b;
  return x;
}

void startupcpp() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
}

double distance(ddatas x, ddatas y) {
  double a, b;
  a = x.first - y.first;
  b = x.second - y.second;
  return sqrt(a * a + b * b);
}

ll modinv(ll a) {
  ll b = mod, u = 1, v = 0, t;
  while (b) {
    t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  return (u + mod) % mod;
}

ll moddevide(ll a, ll b) { return (a * modinv(b)) % mod; }

vec modncrlistp, modncrlistm;

ll modncr(ll n, ll r) {
  ll i, size = modncrlistp.size();
  if (size <= n) {
    modncrlistp.resize(n + 1);
    modncrlistm.resize(n + 1);
    if (!size) {
      modncrlistp[0] = modncrlistm[0] = 1;
      size++;
    }
    For(i, size, n + 1) {
      modncrlistp[i] = modncrlistp[i - 1] * i % mod;
      modncrlistm[i] = modinv(modncrlistp[i]);
    }
  }
  return modncrlistp[n] * modncrlistm[r] % mod * modncrlistm[n - r] % mod;
}

ll modpow(ll a, ll n) {
  ll res = 1;
  while (n) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

ll gcd(ll a, ll b) {
  if (!b)
    return a;
  return (a % b == 0) ? b : gcd(b, a % b);
}
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

ll countdigits(ll n) {
  ll ans = 0;
  while (n) {
    n /= 10;
    ans++;
  }
  return ans;
}

ll sumdigits(ll n) {
  ll ans = 0;
  while (n) {
    ans += n % 10;
    n /= 10;
  }
  return ans;
}

struct segtree {
  ll N, E;
  using func = function<ll(ll, ll)>;
  func f;
  vec tree;
  segtree(vec &v, ll e, func F) : E(e), f(F) {
    ll i, K = v.size();
    N = 1;
    while (N < K)
      N *= 2;
    tree.resize(2 * N - 1);
    For(i, N - 1, N - 1 + K) tree[i] = v[i - N + 1];
    For(i, N + K - 1, 2 * N - 1) tree[i] = E;
    brep(i, N - 1) tree[i] = f(tree[i * 2 + 1], tree[i * 2 + 2]);
  }
  void input(ll i, ll a) {
    i += N - 1;
    tree[i] = a;
    while (i) {
      i = (i - 1) / 2;
      tree[i] = f(tree[i * 2 + 1], tree[i * 2 + 2]);
    }
  }
  ll res(ll a, ll b, ll k, ll l, ll r) {
    if (r <= a || b <= l)
      return E;
    if (a <= l && r <= b)
      return tree[k];
    return f(res(a, b, 2 * k + 1, l, (l + r) / 2),
             res(a, b, 2 * k + 2, (l + r) / 2, r));
  }
  ll q(ll a, ll b) { return res(a, b, 0, 0, N); }
  void prt() { output(tree); }
};

struct unionfind {
  vec par, treesize;
  unionfind(ll N) : par(N) {
    ll i;
    rep(i, N) par[i] = i;
    treesize.resize(N, 1);
  }
  ll root(ll x) {
    ll r;
    if (par[x] == x)
      return x;
    r = root(par[x]);
    if (par[x] != r) {
      treesize[r] += treesize[x];
      treesize[x] = 0;
      par[x] = r;
    }
    return r;
  }
  bool unite(ll x, ll y) {
    ll px = root(x);
    ll py = root(y);
    if (px != py) {
      par[px] = py;
      treesize[py] += treesize[px];
      treesize[px] = 0;
    }
    return px != py;
  }
  bool parcheck(ll x, ll y) {
    ll px = root(x);
    ll py = root(y);
    return px == py;
  }
  ll size(ll x) {
    ll px = root(x);
    return treesize[px];
  }
  void clear() {
    ll i;
    rep(i, (ll)par.size()) {
      par[i] = i;
      treesize[i] = 1;
    }
  }
};

int main() {
  startupcpp();
  // ll test;cin>>test;while(test--){
  ll i, j, k, N, M, K, f, cnt;
  cin >> N >> K;
  vector<double> x(N), y(N), c(N), r(N);
  rep(i, N) cin >> x[i] >> y[i] >> c[i];
  double ans = 10000000, ng = 0, mid;
  while (ans - ng > eps) {
    mid = (ans + ng) / 2;
    f = 0;
    rep(i, N) r[i] = mid / c[i];
    rep(i, N) {
      cnt = 1;
      rep(k, N) {
        if (i == k)
          continue;
        if (distance(ddatas(x[k], y[k]), ddatas(x[i], y[i])) <= r[k] + eps)
          cnt++;
      }
      if (cnt >= K) {
        f = 1;
        break;
      }
      For(j, i + 1, N) {
        if (distance(ddatas(x[i], y[i]), ddatas(x[j], y[j])) >
            r[i] + r[j] + eps)
          continue;
        double ansx, ansy, a, rot, kx, ky;
        kx = x[i] - x[j];
        ky = y[i] - y[j];
        a = kx * kx + ky * ky - r[i] * r[i] + r[j] * r[j];
        a /= 2;
        rot = sqrt((kx * kx + ky * ky) * r[j] * r[j] - a * a);
        ansx = x[j] + (a * kx + ky * rot) / (kx * kx + ky * ky);
        ansy = y[j] + (a * ky - kx * rot) / (kx * kx + ky * ky);
        cnt = 2;
        rep(k, N) {
          if (i == k || j == k)
            continue;
          if (distance(ddatas(x[k], y[k]), ddatas(ansx, ansy)) <= r[k] + eps)
            cnt++;
        }
        if (cnt >= K) {
          i = N;
          f = 1;
          break;
        }
        ansx = x[j] + (a * kx - ky * rot) / (kx * kx + ky * ky);
        ansy = y[j] + (a * ky + kx * rot) / (kx * kx + ky * ky);
        cnt = 2;
        rep(k, N) {
          if (i == k || j == k)
            continue;
          if (distance(ddatas(x[k], y[k]), ddatas(ansx, ansy)) <= r[k] + eps)
            cnt++;
        }
        if (cnt >= K) {
          i = N;
          f = 1;
          break;
        }
      }
    }
    if (f) {
      ans = mid;
    } else {
      ng = mid;
    }
  }
  print(ans);
  return 0;
}

Fixed submission:
#pragma GCC optimize("Ofast")
#include <bits/stdc++.h>
// #include<ext/pb_ds/assoc_container.hpp>
// #include<ext/pb_ds/tree_policy.hpp>
// #include<ext/pb_ds/tag_and_trait.hpp>
// using namespace __gnu_pbds;
using namespace std;
using ll = long long;
// #define double long double
using datas = pair<ll, ll>;
using ddatas = pair<double, double>;
using tdata = pair<ll, datas>;
using vec = vector<ll>;
using mat = vector<vec>;
using pvec = vector<datas>;
using pmat = vector<pvec>;
// using
// llset=tree<ll,null_type,less<ll>,rb_tree_tag,tree_order_statistics_node_update>;
#define For(i, a, b) for (i = a; i < (ll)b; i++)
#define bFor(i, a, b) for (i = a; i >= (ll)b; i--)
#define rep(i, N) For(i, 0, N)
#define rep1(i, N) For(i, 1, N)
#define brep(i, N) bFor(i, N - 1, 0)
#define all(v) (v).begin(), (v).end()
#define allr(v) (v).rbegin(), (v).rend()
#define vsort(v) sort(all(v))
#define vrsort(v) sort(allr(v))
#define endl "\n"
#define pb push_back
#define eb emplace_back
#define print(v) cout << v << endl
#define printyes cout << "Yes" << endl
#define printno cout << "No" << endl
#define printYES cout << "YES" << endl
#define printNO cout << "NO" << endl
#define output(v)                                                              \
  do {                                                                         \
    bool f = 0;                                                                \
    for (auto outi : v) {                                                      \
      cout << (f ? " " : "") << outi;                                          \
      f = 1;                                                                   \
    }                                                                          \
    cout << endl;                                                              \
  } while (0)
const ll mod = 1000000007;
const ll inf = 1LL << 60;
const double PI = acos(-1);
const double eps = 1e-9;
template <class T> inline bool chmax(T &a, T b) {
  bool x = a < b;
  if (x)
    a = b;
  return x;
}
template <class T> inline bool chmin(T &a, T b) {
  bool x = a > b;
  if (x)
    a = b;
  return x;
}

void startupcpp() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  cout << fixed << setprecision(15);
}

double distance(ddatas x, ddatas y) {
  double a, b;
  a = x.first - y.first;
  b = x.second - y.second;
  return sqrt(a * a + b * b);
}

ll modinv(ll a) {
  ll b = mod, u = 1, v = 0, t;
  while (b) {
    t = a / b;
    a -= t * b;
    swap(a, b);
    u -= t * v;
    swap(u, v);
  }
  return (u + mod) % mod;
}

ll moddevide(ll a, ll b) { return (a * modinv(b)) % mod; }

vec modncrlistp, modncrlistm;

ll modncr(ll n, ll r) {
  ll i, size = modncrlistp.size();
  if (size <= n) {
    modncrlistp.resize(n + 1);
    modncrlistm.resize(n + 1);
    if (!size) {
      modncrlistp[0] = modncrlistm[0] = 1;
      size++;
    }
    For(i, size, n + 1) {
      modncrlistp[i] = modncrlistp[i - 1] * i % mod;
      modncrlistm[i] = modinv(modncrlistp[i]);
    }
  }
  return modncrlistp[n] * modncrlistm[r] % mod * modncrlistm[n - r] % mod;
}

ll modpow(ll a, ll n) {
  ll res = 1;
  while (n) {
    if (n & 1)
      res = res * a % mod;
    a = a * a % mod;
    n >>= 1;
  }
  return res;
}

ll gcd(ll a, ll b) {
  if (!b)
    return a;
  return (a % b == 0) ? b : gcd(b, a % b);
}
ll lcm(ll a, ll b) { return a / gcd(a, b) * b; }

ll countdigits(ll n) {
  ll ans = 0;
  while (n) {
    n /= 10;
    ans++;
  }
  return ans;
}

ll sumdigits(ll n) {
  ll ans = 0;
  while (n) {
    ans += n % 10;
    n /= 10;
  }
  return ans;
}

struct segtree {
  ll N, E;
  using func = function<ll(ll, ll)>;
  func f;
  vec tree;
  segtree(vec &v, ll e, func F) : E(e), f(F) {
    ll i, K = v.size();
    N = 1;
    while (N < K)
      N *= 2;
    tree.resize(2 * N - 1);
    For(i, N - 1, N - 1 + K) tree[i] = v[i - N + 1];
    For(i, N + K - 1, 2 * N - 1) tree[i] = E;
    brep(i, N - 1) tree[i] = f(tree[i * 2 + 1], tree[i * 2 + 2]);
  }
  void input(ll i, ll a) {
    i += N - 1;
    tree[i] = a;
    while (i) {
      i = (i - 1) / 2;
      tree[i] = f(tree[i * 2 + 1], tree[i * 2 + 2]);
    }
  }
  ll res(ll a, ll b, ll k, ll l, ll r) {
    if (r <= a || b <= l)
      return E;
    if (a <= l && r <= b)
      return tree[k];
    return f(res(a, b, 2 * k + 1, l, (l + r) / 2),
             res(a, b, 2 * k + 2, (l + r) / 2, r));
  }
  ll q(ll a, ll b) { return res(a, b, 0, 0, N); }
  void prt() { output(tree); }
};

struct unionfind {
  vec par, treesize;
  unionfind(ll N) : par(N) {
    ll i;
    rep(i, N) par[i] = i;
    treesize.resize(N, 1);
  }
  ll root(ll x) {
    ll r;
    if (par[x] == x)
      return x;
    r = root(par[x]);
    if (par[x] != r) {
      treesize[r] += treesize[x];
      treesize[x] = 0;
      par[x] = r;
    }
    return r;
  }
  bool unite(ll x, ll y) {
    ll px = root(x);
    ll py = root(y);
    if (px != py) {
      par[px] = py;
      treesize[py] += treesize[px];
      treesize[px] = 0;
    }
    return px != py;
  }
  bool parcheck(ll x, ll y) {
    ll px = root(x);
    ll py = root(y);
    return px == py;
  }
  ll size(ll x) {
    ll px = root(x);
    return treesize[px];
  }
  void clear() {
    ll i;
    rep(i, (ll)par.size()) {
      par[i] = i;
      treesize[i] = 1;
    }
  }
};

int main() {
  startupcpp();
  // ll test;cin>>test;while(test--){
  ll i, j, k, N, M, K, f, cnt;
  cin >> N >> K;
  vector<double> x(N), y(N), c(N), r(N);
  rep(i, N) cin >> x[i] >> y[i] >> c[i];
  double ans = 10000000, ng = 0, mid;
  while (ans - ng > eps) {
    mid = (ans + ng) / 2;
    f = 0;
    rep(i, N) r[i] = mid / c[i];
    rep(i, N) {
      cnt = 1;
      rep(k, N) {
        if (i == k)
          continue;
        if (distance(ddatas(x[k], y[k]), ddatas(x[i], y[i])) <= r[k] + eps)
          cnt++;
      }
      if (cnt >= K) {
        f = 1;
        break;
      }
      For(j, i + 1, N) {
        if (distance(ddatas(x[i], y[i]), ddatas(x[j], y[j])) >
            r[i] + r[j] + eps)
          continue;
        double ansx, ansy, a, rot, kx, ky;
        kx = x[i] - x[j];
        ky = y[i] - y[j];
        a = kx * kx + ky * ky - r[i] * r[i] + r[j] * r[j];
        a /= 2;
        rot = sqrt((kx * kx + ky * ky) * r[j] * r[j] - a * a);
        ansx = x[j] + (a * kx + ky * rot) / (kx * kx + ky * ky);
        ansy = y[j] + (a * ky - kx * rot) / (kx * kx + ky * ky);
        cnt = 2;
        rep(k, N) {
          if (i == k || j == k)
            continue;
          if (distance(ddatas(x[k], y[k]), ddatas(ansx, ansy)) <= r[k] + eps)
            cnt++;
        }
        if (cnt >= K) {
          i = N;
          f = 1;
          break;
        }
        ansx = x[j] + (a * kx - ky * rot) / (kx * kx + ky * ky);
        ansy = y[j] + (a * ky + kx * rot) / (kx * kx + ky * ky);
        cnt = 2;
        rep(k, N) {
          if (i == k || j == k)
            continue;
          if (distance(ddatas(x[k], y[k]), ddatas(ansx, ansy)) <= r[k] + eps)
            cnt++;
        }
        if (cnt >= K) {
          i = N;
          f = 1;
          break;
        }
      }
    }
    if (f) {
      ans = mid;
    } else {
      ng = mid;
    }
  }
  print(ans);
  return 0;
}