convex/fenchel.hpp

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• Last update: 2024-09-24 18:06:42+09:00
• Include: #include "convex/fenchel.hpp"

Depends on

• geo/base.hpp
• geo/convex_hull.hpp

Verified with

• test/5_atcoder/arc130f.test.cpp

Code

#include "geo/convex_hull.hpp"
#include "geo/base.hpp"

// (L,R,a,b)：傾きが [L,R) のとき (a,b) を通る
template <typename T>
vc<tuple<T, T, T, T>> Fenchel(vc<Point<T>> XY, string mode, bool sorted) {
  if (mode == "upper") {
    for (auto&& p: XY) p.y = -p.y;
    vc<tuple<T, T, T, T>> res;
    for (auto&& [L, R, a, b]: Fenchel(XY, "lower", sorted)) {
      T l = (R == infty<T> ? -infty<T> : 1 - R);
      T r = (L == -infty<T> ? infty<T> : 1 - L);
      chmax(l, -infty<T>), chmin(r, infty<T>);
      res.eb(l, r, a, -b);
    }
    reverse(all(res));
    return res;
  }
  auto I = ConvexHull(XY, "lower", sorted);
  XY = rearrange(XY, I);
  vc<tuple<T, T, T, T>> res;

  ll lo = -infty<ll>;
  FOR(i, len(XY)) {
    T hi = infty<T>;
    if (i + 1 < len(XY)) {
      chmin(hi, floor(XY[i + 1].y - XY[i].y, XY[i + 1].x - XY[i].x) + 1);
    };
    if (lo < hi) res.eb(lo, hi, XY[i].x, XY[i].y);
    lo = hi;
  }
  return res;
}

#line 2 "geo/convex_hull.hpp"

#line 2 "geo/base.hpp"
template <typename T>
struct Point {
  T x, y;

  Point() : x(0), y(0) {}

  template <typename A, typename B>
  Point(A x, B y) : x(x), y(y) {}

  template <typename A, typename B>
  Point(pair<A, B> p) : x(p.fi), y(p.se) {}

  Point operator+=(const Point p) {
    x += p.x, y += p.y;
    return *this;
  }
  Point operator-=(const Point p) {
    x -= p.x, y -= p.y;
    return *this;
  }
  Point operator+(Point p) const { return {x + p.x, y + p.y}; }
  Point operator-(Point p) const { return {x - p.x, y - p.y}; }
  bool operator==(Point p) const { return x == p.x && y == p.y; }
  bool operator!=(Point p) const { return x != p.x || y != p.y; }
  Point operator-() const { return {-x, -y}; }
  Point operator*(T t) const { return {x * t, y * t}; }
  Point operator/(T t) const { return {x / t, y / t}; }

  bool operator<(Point p) const {
    if (x != p.x) return x < p.x;
    return y < p.y;
  }
  T dot(Point other) { return x * other.x + y * other.y; }
  T det(Point other) { return x * other.y - y * other.x; }

  double norm() { return sqrtl(x * x + y * y); }
  double angle() { return atan2(y, x); }

  Point rotate(double theta) {
    static_assert(!is_integral<T>::value);
    double c = cos(theta), s = sin(theta);
    return Point{c * x - s * y, s * x + c * y};
  }
};

#ifdef FASTIO
template <typename T>
void rd(Point<T> &p) {
  fastio::rd(p.x), fastio::rd(p.y);
}
template <typename T>
void wt(Point<T> &p) {
  fastio::wt(p.x);
  fastio::wt(' ');
  fastio::wt(p.y);
}
#endif

// A -> B -> C と進むときに、左に曲がるならば +1、右に曲がるならば -1
template <typename T>
int ccw(Point<T> A, Point<T> B, Point<T> C) {
  T x = (B - A).det(C - A);
  if (x > 0) return 1;
  if (x < 0) return -1;
  return 0;
}

template <typename REAL, typename T, typename U>
REAL dist(Point<T> A, Point<U> B) {
  REAL dx = REAL(A.x) - REAL(B.x);
  REAL dy = REAL(A.y) - REAL(B.y);
  return sqrt(dx * dx + dy * dy);
}

// ax+by+c
template <typename T>
struct Line {
  T a, b, c;

  Line(T a, T b, T c) : a(a), b(b), c(c) {}
  Line(Point<T> A, Point<T> B) { a = A.y - B.y, b = B.x - A.x, c = A.x * B.y - A.y * B.x; }
  Line(T x1, T y1, T x2, T y2) : Line(Point<T>(x1, y1), Point<T>(x2, y2)) {}

  template <typename U>
  U eval(Point<U> P) {
    return a * P.x + b * P.y + c;
  }

  template <typename U>
  T eval(U x, U y) {
    return a * x + b * y + c;
  }

  // 同じ直線が同じ a,b,c で表現されるようにする
  void normalize() {
    static_assert(is_same_v<T, int> || is_same_v<T, long long>);
    T g = gcd(gcd(abs(a), abs(b)), abs(c));
    a /= g, b /= g, c /= g;
    if (b < 0) { a = -a, b = -b, c = -c; }
    if (b == 0 && a < 0) { a = -a, b = -b, c = -c; }
  }

  bool is_parallel(Line other) { return a * other.b - b * other.a == 0; }
  bool is_orthogonal(Line other) { return a * other.a + b * other.b == 0; }
};

template <typename T>
struct Segment {
  Point<T> A, B;

  Segment(Point<T> A, Point<T> B) : A(A), B(B) {}
  Segment(T x1, T y1, T x2, T y2) : Segment(Point<T>(x1, y1), Point<T>(x2, y2)) {}

  bool contain(Point<T> C) {
    T det = (C - A).det(B - A);
    if (det != 0) return 0;
    return (C - A).dot(B - A) >= 0 && (C - B).dot(A - B) >= 0;
  }

  Line<T> to_Line() { return Line(A, B); }
};

template <typename REAL>
struct Circle {
  Point<REAL> O;
  REAL r;
  Circle(Point<REAL> O, REAL r) : O(O), r(r) {}
  Circle(REAL x, REAL y, REAL r) : O(x, y), r(r) {}
  template <typename T>
  bool contain(Point<T> p) {
    REAL dx = p.x - O.x, dy = p.y - O.y;
    return dx * dx + dy * dy <= r * r;
  }
};
#line 4 "geo/convex_hull.hpp"

// allow_180=true で同一座標点があるとこわれる
// full なら I[0] が sorted で min になる
template <typename T, bool allow_180 = false>
vector<int> ConvexHull(vector<Point<T>>& XY, string mode = "full", bool sorted = false) {
  assert(mode == "full" || mode == "lower" || mode == "upper");
  ll N = XY.size();
  if (N == 1) return {0};
  if (N == 2) {
    if (XY[0] < XY[1]) return {0, 1};
    if (XY[1] < XY[0]) return {1, 0};
    return {0};
  }
  vc<int> I(N);
  if (sorted) {
    FOR(i, N) I[i] = i;
  } else {
    I = argsort(XY);
  }
  if constexpr (allow_180) { FOR(i, N - 1) assert(XY[i] != XY[i + 1]); }

  auto check = [&](ll i, ll j, ll k) -> bool {
    T det = (XY[j] - XY[i]).det(XY[k] - XY[i]);
    if constexpr (allow_180) return det >= 0;
    return det > T(0);
  };

  auto calc = [&]() {
    vector<int> P;
    for (auto&& k: I) {
      while (P.size() > 1) {
        auto i = P[P.size() - 2];
        auto j = P[P.size() - 1];
        if (check(i, j, k)) break;
        P.pop_back();
      }
      P.eb(k);
    }
    return P;
  };

  vc<int> P;
  if (mode == "full" || mode == "lower") {
    vc<int> Q = calc();
    P.insert(P.end(), all(Q));
  }
  if (mode == "full" || mode == "upper") {
    if (!P.empty()) P.pop_back();
    reverse(all(I));
    vc<int> Q = calc();
    P.insert(P.end(), all(Q));
  }
  if (mode == "upper") reverse(all(P));
  while (len(P) >= 2 && XY[P[0]] == XY[P.back()]) P.pop_back();
  return P;
}
#line 3 "convex/fenchel.hpp"

// (L,R,a,b)：傾きが [L,R) のとき (a,b) を通る
template <typename T>
vc<tuple<T, T, T, T>> Fenchel(vc<Point<T>> XY, string mode, bool sorted) {
  if (mode == "upper") {
    for (auto&& p: XY) p.y = -p.y;
    vc<tuple<T, T, T, T>> res;
    for (auto&& [L, R, a, b]: Fenchel(XY, "lower", sorted)) {
      T l = (R == infty<T> ? -infty<T> : 1 - R);
      T r = (L == -infty<T> ? infty<T> : 1 - L);
      chmax(l, -infty<T>), chmin(r, infty<T>);
      res.eb(l, r, a, -b);
    }
    reverse(all(res));
    return res;
  }
  auto I = ConvexHull(XY, "lower", sorted);
  XY = rearrange(XY, I);
  vc<tuple<T, T, T, T>> res;

  ll lo = -infty<ll>;
  FOR(i, len(XY)) {
    T hi = infty<T>;
    if (i + 1 < len(XY)) {
      chmin(hi, floor(XY[i + 1].y - XY[i].y, XY[i + 1].x - XY[i].x) + 1);
    };
    if (lo < hi) res.eb(lo, hi, XY[i].x, XY[i].y);
    lo = hi;
  }
  return res;
}

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