Problem p01128 (C++)

Buggy submission (status: Runtime Error):
#include <bits/stdc++.h>

using namespace std;

#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)

// ???/????????????
struct Point {
  double x, y;
  Point(double x = 0.0, double y = 0.0) : x(x), y(y) {}

  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(x * a, y * a); }
  Point operator/(double a) { return Point(x / a, y / a); }

  double abs() { return sqrt(norm()); }
  double norm() { return x * x + y * y; }

  bool operator<(const Point &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const Point &p) const {
    return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
  }
};
typedef Point Vector;

// ??????/??´???
struct Segment {
  Point p1, p2;
};
typedef Segment Line;

// ????????????????????????
double norm(Vector v) { return v.x * v.x + v.y * v.y; }
// ?????????????????§??????
double abs(Vector v) { return sqrt(norm(v)); }
// ?????????????????????
double dot(Vector a, Vector b) { return a.x * b.x + a.y * b.y; }
// ??????????????????????????§??????
double cross(Vector a, Vector b) { return a.x * b.y - a.y * b.x; }
// ??´?????????
bool isOrthogonal(Vector a, Vector b) { return equals(dot(a, b), 0.0); }
bool isOrthogonal(Point a1, Point a2, Point b1, Point b2) {
  return isOrthogonal(a1 - a2, b1 - b2);
}
bool isOrthogonal(Segment s1, Segment s2) {
  return equals(dot(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
// ????????????
bool isParallel(Vector a, Vector b) { return equals(cross(a, b), 0.0); }
bool isParallel(Point a1, Point a2, Point b1, Point b2) {
  return isParallel(a1 - a2, b1 - b2);
}
bool isParallel(Segment s1, Segment s2) {
  return equals(cross(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
// ?°???±
Point project(Segment s, Point p) {
  Vector base = s.p2 - s.p1;
  double r = dot(p - s.p1, base) / norm(base);
  return s.p1 + base * r;
}
// ????°?
Point reflect(Segment s, Point p) { return p + (project(s, p) - p) * 2.0; }
static const int COUNTER_CLOCKWISE = 1;
static const int CLOCKWISE = -1;
static const int ONLINE_BACK = 2;
static const int ONLINE_FRONT = -2;
static const int ON_SEGMENT = 0;
// ???????¨???????
int ccw(Point p0, Point p1, Point p2) {
  Vector a = p1 - p0;
  Vector b = p2 - p0;
  if (cross(a, b) > EPS)
    return COUNTER_CLOCKWISE;
  if (cross(a, b) < -EPS)
    return CLOCKWISE;
  if (dot(a, b) < -EPS)
    return ONLINE_BACK;
  if (a.norm() < b.norm())
    return ONLINE_FRONT;
  return ON_SEGMENT;
}
// ????????????
bool intersect(Point p1, Point p2, Point p3, Point p4) {
  return (ccw(p1, p2, p3) * ccw(p1, p2, p4) <= 0 &&
          ccw(p3, p4, p1) * ccw(p3, p4, p2) <= 0);
}
bool intersect(Segment s1, Segment s2) {
  return intersect(s1.p1, s1.p2, s2.p1, s2.p2);
}
// ?????????????????¢
double getDistance(Point a, Point b) { return abs(a - b); }
// ??´?????¨?????¨????????¢
double getDistanceLP(Line l, Point p) {
  return abs(cross(l.p2 - l.p1, p - l.p1) / abs(l.p2 - l.p1));
}
// ????????¨?????¨????????¢
double getDistanceSP(Segment s, Point p) {
  if (dot(s.p2 - s.p1, p - s.p1) < 0.0)
    return abs(p - s.p1);
  if (dot(s.p1 - s.p2, p - s.p2) < 0.0)
    return abs(p - s.p2);
  return getDistanceLP(s, p);
}
// ????????????????????¢
double getDistance(Segment s1, Segment s2) {
  if (intersect(s1, s2))
    return 0.0;
  return min(min(getDistanceSP(s1, s2.p1), getDistanceSP(s1, s2.p2)),
             min(getDistanceSP(s2, s1.p1), getDistanceSP(s2, s1.p2)));
}
// ???????????????
Point getCrossPoint(Segment s1, Segment s2) {
  Vector base = s2.p2 - s2.p1;
  double d1 = abs(cross(base, s1.p1 - s2.p1));
  double d2 = abs(cross(base, s1.p2 - s2.p1));
  double t = d1 / (d1 + d2);
  return s1.p1 + (s1.p2 - s1.p1) * t;
}

typedef pair<double, int> P;

int main() {
  int T;
  cin >> T;
  while (T--) {
    Segment ab;
    cin >> ab.p1.x >> ab.p1.y >> ab.p2.x >> ab.p2.y;

    int n;
    cin >> n;
    vector<Segment> s(n);
    vector<int> o(n), l(n);
    for (int i = 0; i < n; i++) {
      cin >> s[i].p1.x >> s[i].p1.y >> s[i].p2.x >> s[i].p2.y >> o[i] >> l[i];
    }

    vector<P> isct_s;
    for (int i = 0; i < n; i++) {
      if (!intersect(ab, s[i]) || isParallel(ab, s[i]))
        continue;
      double dist = getDistance(ab.p1, getCrossPoint(ab, s[i]));
      isct_s.push_back(P(dist, i));
    }
    sort(isct_s.begin(), isct_s.end());

    int level =
        (o[isct_s[0].second] ? l[isct_s[0].second] : !l[isct_s[0].second]);
    int ans = 0;
    for (int i = 1; i < isct_s.size(); i++) {
      if (o[isct_s[i].second] == 1 && level != l[isct_s[i].second] ||
          o[isct_s[i].second] == 0 && level == l[isct_s[i].second])
        ans++, level = !level;
    }
    cout << ans << endl;
  }
  return 0;
}

Fixed submission:
#include <bits/stdc++.h>

using namespace std;

#define EPS (1e-10)
#define equals(a, b) (fabs((a) - (b)) < EPS)

// ???/????????????
struct Point {
  double x, y;
  Point(double x = 0.0, double y = 0.0) : x(x), y(y) {}

  Point operator+(Point p) { return Point(x + p.x, y + p.y); }
  Point operator-(Point p) { return Point(x - p.x, y - p.y); }
  Point operator*(double a) { return Point(x * a, y * a); }
  Point operator/(double a) { return Point(x / a, y / a); }

  double abs() { return sqrt(norm()); }
  double norm() { return x * x + y * y; }

  bool operator<(const Point &p) const { return x != p.x ? x < p.x : y < p.y; }
  bool operator==(const Point &p) const {
    return fabs(x - p.x) < EPS && fabs(y - p.y) < EPS;
  }
};
typedef Point Vector;

// ??????/??´???
struct Segment {
  Point p1, p2;
};
typedef Segment Line;

// ????????????????????????
double norm(Vector v) { return v.x * v.x + v.y * v.y; }
// ?????????????????§??????
double abs(Vector v) { return sqrt(norm(v)); }
// ?????????????????????
double dot(Vector a, Vector b) { return a.x * b.x + a.y * b.y; }
// ??????????????????????????§??????
double cross(Vector a, Vector b) { return a.x * b.y - a.y * b.x; }
// ??´?????????
bool isOrthogonal(Vector a, Vector b) { return equals(dot(a, b), 0.0); }
bool isOrthogonal(Point a1, Point a2, Point b1, Point b2) {
  return isOrthogonal(a1 - a2, b1 - b2);
}
bool isOrthogonal(Segment s1, Segment s2) {
  return equals(dot(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
// ????????????
bool isParallel(Vector a, Vector b) { return equals(cross(a, b), 0.0); }
bool isParallel(Point a1, Point a2, Point b1, Point b2) {
  return isParallel(a1 - a2, b1 - b2);
}
bool isParallel(Segment s1, Segment s2) {
  return equals(cross(s1.p2 - s1.p1, s2.p2 - s2.p1), 0.0);
}
// ?°???±
Point project(Segment s, Point p) {
  Vector base = s.p2 - s.p1;
  double r = dot(p - s.p1, base) / norm(base);
  return s.p1 + base * r;
}
// ????°?
Point reflect(Segment s, Point p) { return p + (project(s, p) - p) * 2.0; }
static const int COUNTER_CLOCKWISE = 1;
static const int CLOCKWISE = -1;
static const int ONLINE_BACK = 2;
static const int ONLINE_FRONT = -2;
static const int ON_SEGMENT = 0;
// ???????¨???????
int ccw(Point p0, Point p1, Point p2) {
  Vector a = p1 - p0;
  Vector b = p2 - p0;
  if (cross(a, b) > EPS)
    return COUNTER_CLOCKWISE;
  if (cross(a, b) < -EPS)
    return CLOCKWISE;
  if (dot(a, b) < -EPS)
    return ONLINE_BACK;
  if (a.norm() < b.norm())
    return ONLINE_FRONT;
  return ON_SEGMENT;
}
// ????????????
bool intersect(Point p1, Point p2, Point p3, Point p4) {
  return (ccw(p1, p2, p3) * ccw(p1, p2, p4) <= 0 &&
          ccw(p3, p4, p1) * ccw(p3, p4, p2) <= 0);
}
bool intersect(Segment s1, Segment s2) {
  return intersect(s1.p1, s1.p2, s2.p1, s2.p2);
}
// ?????????????????¢
double getDistance(Point a, Point b) { return abs(a - b); }
// ??´?????¨?????¨????????¢
double getDistanceLP(Line l, Point p) {
  return abs(cross(l.p2 - l.p1, p - l.p1) / abs(l.p2 - l.p1));
}
// ????????¨?????¨????????¢
double getDistanceSP(Segment s, Point p) {
  if (dot(s.p2 - s.p1, p - s.p1) < 0.0)
    return abs(p - s.p1);
  if (dot(s.p1 - s.p2, p - s.p2) < 0.0)
    return abs(p - s.p2);
  return getDistanceLP(s, p);
}
// ????????????????????¢
double getDistance(Segment s1, Segment s2) {
  if (intersect(s1, s2))
    return 0.0;
  return min(min(getDistanceSP(s1, s2.p1), getDistanceSP(s1, s2.p2)),
             min(getDistanceSP(s2, s1.p1), getDistanceSP(s2, s1.p2)));
}
// ???????????????
Point getCrossPoint(Segment s1, Segment s2) {
  Vector base = s2.p2 - s2.p1;
  double d1 = abs(cross(base, s1.p1 - s2.p1));
  double d2 = abs(cross(base, s1.p2 - s2.p1));
  double t = d1 / (d1 + d2);
  return s1.p1 + (s1.p2 - s1.p1) * t;
}

typedef pair<double, int> P;

int main() {
  int T;
  cin >> T;
  while (T--) {
    Segment ab;
    cin >> ab.p1.x >> ab.p1.y >> ab.p2.x >> ab.p2.y;

    int n;
    cin >> n;
    vector<Segment> s(n);
    vector<int> o(n), l(n);
    for (int i = 0; i < n; i++) {
      cin >> s[i].p1.x >> s[i].p1.y >> s[i].p2.x >> s[i].p2.y >> o[i] >> l[i];
    }

    vector<P> isct_s;
    for (int i = 0; i < n; i++) {
      if (!intersect(ab, s[i]) || isParallel(ab, s[i]))
        continue;
      double dist = getDistance(ab.p1, getCrossPoint(ab, s[i]));
      isct_s.push_back(P(dist, i));
    }
    sort(isct_s.begin(), isct_s.end());

    if (isct_s.empty()) {
      cout << 0 << endl;
      continue;
    }

    int level =
        (o[isct_s[0].second] ? l[isct_s[0].second] : !l[isct_s[0].second]);
    int ans = 0;
    for (int i = 1; i < isct_s.size(); i++) {
      if (o[isct_s[i].second] == 1 && level != l[isct_s[i].second] ||
          o[isct_s[i].second] == 0 && level == l[isct_s[i].second])
        ans++, level = !level;
    }
    cout << ans << endl;
  }
  return 0;
}