Problem p00090 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>
using namespace std;
#define FOR(i, k, n) for (int i = (k); i < (n); i++)
#define REP(i, n) FOR(i, 0, n)
#define ALL(a) begin(a), end(a)
#define MS(m, v) memset(m, v, sizeof(m))
#define D10 fixed << setprecision(10)
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> P;
typedef long long ll;
const int INF = 114514810;
const int MOD = 1000000007;
const double EPS = 1e-10;
struct edge {
  int to, cost;
  bool operator<(const edge &e) const { return cost < e.cost; }
  bool operator>(const edge &e) const { return cost > e.cost; }
};
int dx[] = {-1, 0, 0, 1};
int dy[] = {0, -1, 1, 0};
template <class T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <class T> T &chmax(T &a, const T &b) { return a = max(a, b); }
bool valid(int x, int y, int h, int w) {
  return (x >= 0 && y >= 0 && x < h && y < w);
}
int place(int x, int y, int w) { return w * x + y; }
///*************************************************************************************///
///*************************************************************************************///
///*************************************************************************************///

const double PI = acos(-1.0);
bool eq(double a, double b) { return fabs(a - b) < EPS; }
typedef complex<double> Point;
typedef vector<Point> Polygon;

namespace std {
bool operator<(const Point &a, const Point &b) {
  return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
}
} // namespace std

struct Line {
  Point a, b;
  Line(Point p, Point q) : a(p), b(q){};
  Line(double x1, double y1, double x2, double y2)
      : a(Point(x1, y1)), b(Point(x2, y2)){};
};

struct Circle {
  Point p;
  double r;
  int n;
  Circle(Point a, double b) : p(a), r(b){};
};

double dot(Point a, Point b) { return real(conj(a) * b); }

double cross(Point a, Point b) { return imag(conj(a) * b); }

int ccw(Point a, Point b, Point c) {
  b -= a;
  c -= a;
  if (cross(b, c) > EPS)
    return 1; // counter cloclwise
  if (cross(b, c) < -EPS)
    return -1; // cloclwise
  if (dot(b, c) < 0)
    return 2; // c--a--b on line
  if (norm(b) < norm(c))
    return -2; // a--b--c on line
  return 0;    // a--c--b on line
}

bool isis_ll(Line l, Line m) { return abs(cross(l.b - l.a, m.b - m.a)) > EPS; }

bool isis_ls(Line l, Line s) {
  return cross(l.b - l.a, s.a - l.a) * cross(l.b - l.a, s.b - l.a) < EPS;
}

bool isis_ss(Line s, Line t) {
  return (ccw(s.a, s.b, t.a) * ccw(s.a, s.b, t.b) <= 0 &&
          ccw(t.a, t.b, s.a) * ccw(t.a, t.b, s.b) <= 0);
}

bool isis_lp(Line l, Point p) { return (abs(cross(l.b - p, l.a - p)) < EPS); }

bool isis_sp(Line s, Point p) {
  return (abs(s.a - p) + abs(s.b - p) - abs(s.b - s.a)) < EPS;
}

Point projection(Line l, Point p) {
  Point base = l.b - l.a;
  double r = dot(p - l.a, base) / norm(base);
  return l.a + base * r;
}

Point mirror(Line l, Point p) { return 2.0 * projection(l, p) - p; }

double dist_lp(Line l, Point p) { return abs(p - projection(l, p)); }

double dist_ll(Line l, Line m) { return isis_ll(l, m) ? 0 : dist_lp(l, m.a); }

double dist_ls(Line l, Line s) {
  if (isis_ls(l, s))
    return 0;
  return min(dist_lp(l, s.a), dist_lp(l, s.b));
}

double dist_sp(Line s, Point p) {
  Point r = projection(s, p);
  if (isis_sp(s, r))
    return abs(r - p);
  return min(abs(s.a - p), abs(s.b - p));
}

double dist_ss(Line s, Line t) {
  if (isis_ss(s, t))
    return 0;
  return min(min(dist_sp(s, t.a), dist_sp(s, t.b)),
             min(dist_sp(t, s.a), dist_sp(t, s.b)));
}

Point is_ll(Line s, Line t) {
  double a = cross(s.b - s.a, t.b - t.a);
  double b = cross(s.b - s.a, s.b - t.a);
  return t.a + b / a * (t.b - t.a);
}

vector<Point> is_cc(Circle c1, Circle c2) {
  vector<Point> res;
  double d = abs(c1.p - c2.p);
  double rc = (d * d + pow(c1.r, 2) - pow(c2.r, 2)) / (2 * d);
  double dfr = pow(c1.r, 2) - rc * rc;
  if (abs(dfr) < EPS)
    dfr = 0;
  if (dfr < 0.0)
    return res;
  double rs = sqrt(dfr);
  Point diff = (c2.p - c1.p) / d;
  res.push_back(c1.p + diff * Point(rc, rs));
  if (dfr != 0.0)
    res.push_back(c1.p + diff * Point(rc, -rs));
  return res;
}

int main() {
  int n;
  while (cin >> n, n) {
    vector<Circle> cs;
    REP(i, n) {
      double x, y;
      char c;
      cin >> x >> c >> y;
      cs.push_back(Circle(Point(x, y), 1));
    }

    vector<Point> ps;
    REP(i, cs.size()) REP(j, i) {
      auto tmp = is_cc(cs[i], cs[j]);
      REP(k, tmp.size()) { ps.push_back(tmp[k]); }
    }
    vi cnt(ps.size());
    REP(i, ps.size()) {
      REP(j, cs.size()) {
        if (abs(ps[i] - cs[j].p) - 1 < EPS) {
          cnt[i]++;
        }
      }
    }
    if (cnt.size() == 0)
      cout << 1 << endl;
    cout << *max_element(ALL(cnt)) << endl;
  }
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>
using namespace std;
#define FOR(i, k, n) for (int i = (k); i < (n); i++)
#define REP(i, n) FOR(i, 0, n)
#define ALL(a) begin(a), end(a)
#define MS(m, v) memset(m, v, sizeof(m))
#define D10 fixed << setprecision(10)
typedef vector<int> vi;
typedef vector<string> vs;
typedef pair<int, int> P;
typedef long long ll;
const int INF = 114514810;
const int MOD = 1000000007;
const double EPS = 1e-10;
struct edge {
  int to, cost;
  bool operator<(const edge &e) const { return cost < e.cost; }
  bool operator>(const edge &e) const { return cost > e.cost; }
};
int dx[] = {-1, 0, 0, 1};
int dy[] = {0, -1, 1, 0};
template <class T> T &chmin(T &a, const T &b) { return a = min(a, b); }
template <class T> T &chmax(T &a, const T &b) { return a = max(a, b); }
bool valid(int x, int y, int h, int w) {
  return (x >= 0 && y >= 0 && x < h && y < w);
}
int place(int x, int y, int w) { return w * x + y; }
///*************************************************************************************///
///*************************************************************************************///
///*************************************************************************************///

const double PI = acos(-1.0);
bool eq(double a, double b) { return fabs(a - b) < EPS; }
typedef complex<double> Point;
typedef vector<Point> Polygon;

namespace std {
bool operator<(const Point &a, const Point &b) {
  return real(a) != real(b) ? real(a) < real(b) : imag(a) < imag(b);
}
} // namespace std

struct Line {
  Point a, b;
  Line(Point p, Point q) : a(p), b(q){};
  Line(double x1, double y1, double x2, double y2)
      : a(Point(x1, y1)), b(Point(x2, y2)){};
};

struct Circle {
  Point p;
  double r;
  int n;
  Circle(Point a, double b) : p(a), r(b){};
};

double dot(Point a, Point b) { return real(conj(a) * b); }

double cross(Point a, Point b) { return imag(conj(a) * b); }

int ccw(Point a, Point b, Point c) {
  b -= a;
  c -= a;
  if (cross(b, c) > EPS)
    return 1; // counter cloclwise
  if (cross(b, c) < -EPS)
    return -1; // cloclwise
  if (dot(b, c) < 0)
    return 2; // c--a--b on line
  if (norm(b) < norm(c))
    return -2; // a--b--c on line
  return 0;    // a--c--b on line
}

bool isis_ll(Line l, Line m) { return abs(cross(l.b - l.a, m.b - m.a)) > EPS; }

bool isis_ls(Line l, Line s) {
  return cross(l.b - l.a, s.a - l.a) * cross(l.b - l.a, s.b - l.a) < EPS;
}

bool isis_ss(Line s, Line t) {
  return (ccw(s.a, s.b, t.a) * ccw(s.a, s.b, t.b) <= 0 &&
          ccw(t.a, t.b, s.a) * ccw(t.a, t.b, s.b) <= 0);
}

bool isis_lp(Line l, Point p) { return (abs(cross(l.b - p, l.a - p)) < EPS); }

bool isis_sp(Line s, Point p) {
  return (abs(s.a - p) + abs(s.b - p) - abs(s.b - s.a)) < EPS;
}

Point projection(Line l, Point p) {
  Point base = l.b - l.a;
  double r = dot(p - l.a, base) / norm(base);
  return l.a + base * r;
}

Point mirror(Line l, Point p) { return 2.0 * projection(l, p) - p; }

double dist_lp(Line l, Point p) { return abs(p - projection(l, p)); }

double dist_ll(Line l, Line m) { return isis_ll(l, m) ? 0 : dist_lp(l, m.a); }

double dist_ls(Line l, Line s) {
  if (isis_ls(l, s))
    return 0;
  return min(dist_lp(l, s.a), dist_lp(l, s.b));
}

double dist_sp(Line s, Point p) {
  Point r = projection(s, p);
  if (isis_sp(s, r))
    return abs(r - p);
  return min(abs(s.a - p), abs(s.b - p));
}

double dist_ss(Line s, Line t) {
  if (isis_ss(s, t))
    return 0;
  return min(min(dist_sp(s, t.a), dist_sp(s, t.b)),
             min(dist_sp(t, s.a), dist_sp(t, s.b)));
}

Point is_ll(Line s, Line t) {
  double a = cross(s.b - s.a, t.b - t.a);
  double b = cross(s.b - s.a, s.b - t.a);
  return t.a + b / a * (t.b - t.a);
}

vector<Point> is_cc(Circle c1, Circle c2) {
  vector<Point> res;
  double d = abs(c1.p - c2.p);
  double rc = (d * d + pow(c1.r, 2) - pow(c2.r, 2)) / (2 * d);
  double dfr = pow(c1.r, 2) - rc * rc;
  if (abs(dfr) < EPS)
    dfr = 0;
  if (dfr < 0.0)
    return res;
  double rs = sqrt(dfr);
  Point diff = (c2.p - c1.p) / d;
  res.push_back(c1.p + diff * Point(rc, rs));
  if (dfr != 0.0)
    res.push_back(c1.p + diff * Point(rc, -rs));
  return res;
}

int main() {
  int n;
  while (cin >> n, n) {
    vector<Circle> cs;
    REP(i, n) {
      double x, y;
      char c;
      cin >> x >> c >> y;
      cs.push_back(Circle(Point(x, y), 1));
    }

    vector<Point> ps;
    REP(i, cs.size()) REP(j, i) {
      auto tmp = is_cc(cs[i], cs[j]);
      REP(k, tmp.size()) { ps.push_back(tmp[k]); }
    }
    vi cnt(ps.size());
    REP(i, ps.size()) {
      REP(j, cs.size()) {
        if (abs(ps[i] - cs[j].p) - 1 < EPS) {
          cnt[i]++;
        }
      }
    }
    if (cnt.size() == 0)
      cout << 1 << endl;
    else
      cout << *max_element(ALL(cnt)) << endl;
  }
  return 0;
}