cp-library

C++ Library for Competitive Programming

View the Project on GitHub emthrm/cp-library

:heavy_check_mark: グラフ/フロー/マッチング/一般グラフの最大マッチング
(test/graph/flow/matching/maximum_matching.test.cpp)

Depends on

Code

/*
 * @title グラフ/フロー/マッチング/一般グラフの最大マッチング
 *
 * verification-helper: PROBLEM http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=3032
 */

#include <cmath>
#include <iostream>
#include <vector>

#include "emthrm/graph/flow/matching/maximum_matching.hpp"

int main() {
  int n, a, b;
  std::cin >> n >> a >> b;
  int ans = 0;
  std::vector<int> as, bs;
  while (n--) {
    int a_i, b_i;
    std::cin >> a_i >> b_i;
    const int x = std::abs(a_i - b_i);
    if (x <= a || (b <= x && x <= 2 * a)) {
      ++ans;
    } else {
      as.emplace_back(a_i);
      bs.emplace_back(b_i);
    }
  }
  n = as.size();
  if (n > 0) {
    std::vector<std::vector<int>> graph(n);
    for (int i = 0; i < n; ++i) {
      for (int j = i + 1; j < n; ++j) {
        const int x = std::abs((as[i] + as[j]) - (bs[i] + bs[j]));
        if (x <= a || (b <= x && x <= 2 * a)) {
          graph[i].emplace_back(j);
          graph[j].emplace_back(i);
        }
      }
    }
    ans += emthrm::maximum_matching(graph);
  }
  std::cout << ans << '\n';
  return 0;
}
#line 1 "test/graph/flow/matching/maximum_matching.test.cpp"
/*
 * @title グラフ/フロー/マッチング/一般グラフの最大マッチング
 *
 * verification-helper: PROBLEM http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=3032
 */

#include <cmath>
#include <iostream>
#include <vector>

#line 1 "include/emthrm/graph/flow/matching/maximum_matching.hpp"



#include <random>
#line 6 "include/emthrm/graph/flow/matching/maximum_matching.hpp"

#line 1 "include/emthrm/math/matrix/gauss_jordan.hpp"



#include <utility>

#line 1 "include/emthrm/math/matrix/matrix.hpp"



#line 5 "include/emthrm/math/matrix/matrix.hpp"

namespace emthrm {

template <typename T>
struct Matrix {
  explicit Matrix(const int m, const int n, const T def = 0)
      : data(m, std::vector<T>(n, def)) {}

  int nrow() const { return data.size(); }
  int ncol() const { return data.empty() ? 0 : data.front().size(); }

  Matrix pow(long long exponent) const {
    const int n = nrow();
    Matrix<T> res(n, n, 0), tmp = *this;
    for (int i = 0; i < n; ++i) {
      res[i][i] = 1;
    }
    for (; exponent > 0; exponent >>= 1) {
      if (exponent & 1) res *= tmp;
      tmp *= tmp;
    }
    return res;
  }

  inline const std::vector<T>& operator[](const int i) const { return data[i]; }
  inline std::vector<T>& operator[](const int i) { return data[i]; }

  Matrix& operator=(const Matrix& x) = default;

  Matrix& operator+=(const Matrix& x) {
    const int m = nrow(), n = ncol();
    for (int i = 0; i < m; ++i) {
      for (int j = 0; j < n; ++j) {
        data[i][j] += x[i][j];
      }
    }
    return *this;
  }

  Matrix& operator-=(const Matrix& x) {
    const int m = nrow(), n = ncol();
    for (int i = 0; i < m; ++i) {
      for (int j = 0; j < n; ++j) {
        data[i][j] -= x[i][j];
      }
    }
    return *this;
  }

  Matrix& operator*=(const Matrix& x) {
    const int m = nrow(), l = ncol(), n = x.ncol();
    std::vector<std::vector<T>> res(m, std::vector<T>(n, 0));
    for (int i = 0; i < m; ++i) {
      for (int k = 0; k < l; ++k) {
        for (int j = 0; j < n; ++j) {
          res[i][j] += data[i][k] * x[k][j];
        }
      }
    }
    data.swap(res);
    return *this;
  }

  Matrix operator+(const Matrix& x) const { return Matrix(*this) += x; }
  Matrix operator-(const Matrix& x) const { return Matrix(*this) -= x; }
  Matrix operator*(const Matrix& x) const { return Matrix(*this) *= x; }

 private:
  std::vector<std::vector<T>> data;
};

}  // namespace emthrm


#line 7 "include/emthrm/math/matrix/gauss_jordan.hpp"

namespace emthrm {

template <bool IS_EXTENDED = false, typename T>
int gauss_jordan(Matrix<T>* a, const T eps = 1e-8) {
  const int m = a->nrow(), n = a->ncol();
  int rank = 0;
  for (int col = 0; col < (IS_EXTENDED ? n - 1 : n); ++col) {
    int pivot = -1;
    T mx = eps;
    for (int row = rank; row < m; ++row) {
      const T abs = ((*a)[row][col] < 0 ? -(*a)[row][col] : (*a)[row][col]);
      if (abs > mx) {
        pivot = row;
        mx = abs;
      }
    }
    if (pivot == -1) continue;
    std::swap((*a)[rank], (*a)[pivot]);
    T tmp = (*a)[rank][col];
    for (int col2 = 0; col2 < n; ++col2) {
      (*a)[rank][col2] /= tmp;
    }
    for (int row = 0; row < m; ++row) {
      if (row != rank &&
          ((*a)[row][col] < 0 ? -(*a)[row][col] : (*a)[row][col]) > eps) {
        tmp = (*a)[row][col];
        for (int col2 = 0; col2 < n; ++col2) {
          (*a)[row][col2] -= (*a)[rank][col2] * tmp;
        }
      }
    }
    ++rank;
  }
  return rank;
}

}  // namespace emthrm


#line 1 "include/emthrm/math/modint.hpp"



#ifndef ARBITRARY_MODINT
# include <cassert>
#endif
#include <compare>
#line 9 "include/emthrm/math/modint.hpp"
// #include <numeric>
#line 12 "include/emthrm/math/modint.hpp"

namespace emthrm {

#ifndef ARBITRARY_MODINT
template <unsigned int M>
struct MInt {
  unsigned int v;

  constexpr MInt() : v(0) {}
  constexpr MInt(const long long x) : v(x >= 0 ? x % M : x % M + M) {}
  static constexpr MInt raw(const int x) {
    MInt x_;
    x_.v = x;
    return x_;
  }

  static constexpr int get_mod() { return M; }
  static constexpr void set_mod(const int divisor) {
    assert(std::cmp_equal(divisor, M));
  }

  static void init(const int x) {
    inv<true>(x);
    fact(x);
    fact_inv(x);
  }

  template <bool MEMOIZES = false>
  static MInt inv(const int n) {
    // assert(0 <= n && n < M && std::gcd(n, M) == 1);
    static std::vector<MInt> inverse{0, 1};
    const int prev = inverse.size();
    if (n < prev) return inverse[n];
    if constexpr (MEMOIZES) {
      // "n!" and "M" must be disjoint.
      inverse.resize(n + 1);
      for (int i = prev; i <= n; ++i) {
        inverse[i] = -inverse[M % i] * raw(M / i);
      }
      return inverse[n];
    }
    int u = 1, v = 0;
    for (unsigned int a = n, b = M; b;) {
      const unsigned int q = a / b;
      std::swap(a -= q * b, b);
      std::swap(u -= q * v, v);
    }
    return u;
  }

  static MInt fact(const int n) {
    static std::vector<MInt> factorial{1};
    if (const int prev = factorial.size(); n >= prev) {
      factorial.resize(n + 1);
      for (int i = prev; i <= n; ++i) {
        factorial[i] = factorial[i - 1] * i;
      }
    }
    return factorial[n];
  }

  static MInt fact_inv(const int n) {
    static std::vector<MInt> f_inv{1};
    if (const int prev = f_inv.size(); n >= prev) {
      f_inv.resize(n + 1);
      f_inv[n] = inv(fact(n).v);
      for (int i = n; i > prev; --i) {
        f_inv[i - 1] = f_inv[i] * i;
      }
    }
    return f_inv[n];
  }

  static MInt nCk(const int n, const int k) {
    if (n < 0 || n < k || k < 0) [[unlikely]] return MInt();
    return fact(n) * (n - k < k ? fact_inv(k) * fact_inv(n - k) :
                                  fact_inv(n - k) * fact_inv(k));
  }
  static MInt nPk(const int n, const int k) {
    return n < 0 || n < k || k < 0 ? MInt() : fact(n) * fact_inv(n - k);
  }
  static MInt nHk(const int n, const int k) {
    return n < 0 || k < 0 ? MInt() : (k == 0 ? 1 : nCk(n + k - 1, k));
  }

  static MInt large_nCk(long long n, const int k) {
    if (n < 0 || n < k || k < 0) [[unlikely]] return MInt();
    inv<true>(k);
    MInt res = 1;
    for (int i = 1; i <= k; ++i) {
      res *= inv(i) * n--;
    }
    return res;
  }

  constexpr MInt pow(long long exponent) const {
    MInt res = 1, tmp = *this;
    for (; exponent > 0; exponent >>= 1) {
      if (exponent & 1) res *= tmp;
      tmp *= tmp;
    }
    return res;
  }

  constexpr MInt& operator+=(const MInt& x) {
    if ((v += x.v) >= M) v -= M;
    return *this;
  }
  constexpr MInt& operator-=(const MInt& x) {
    if ((v += M - x.v) >= M) v -= M;
    return *this;
  }
  constexpr MInt& operator*=(const MInt& x) {
    v = (unsigned long long){v} * x.v % M;
    return *this;
  }
  MInt& operator/=(const MInt& x) { return *this *= inv(x.v); }

  constexpr auto operator<=>(const MInt& x) const = default;

  constexpr MInt& operator++() {
    if (++v == M) [[unlikely]] v = 0;
    return *this;
  }
  constexpr MInt operator++(int) {
    const MInt res = *this;
    ++*this;
    return res;
  }
  constexpr MInt& operator--() {
    v = (v == 0 ? M - 1 : v - 1);
    return *this;
  }
  constexpr MInt operator--(int) {
    const MInt res = *this;
    --*this;
    return res;
  }

  constexpr MInt operator+() const { return *this; }
  constexpr MInt operator-() const { return raw(v ? M - v : 0); }

  constexpr MInt operator+(const MInt& x) const { return MInt(*this) += x; }
  constexpr MInt operator-(const MInt& x) const { return MInt(*this) -= x; }
  constexpr MInt operator*(const MInt& x) const { return MInt(*this) *= x; }
  MInt operator/(const MInt& x) const { return MInt(*this) /= x; }

  friend std::ostream& operator<<(std::ostream& os, const MInt& x) {
    return os << x.v;
  }
  friend std::istream& operator>>(std::istream& is, MInt& x) {
    long long v;
    is >> v;
    x = MInt(v);
    return is;
  }
};
#else  // ARBITRARY_MODINT
template <int ID>
struct MInt {
  unsigned int v;

  constexpr MInt() : v(0) {}
  MInt(const long long x) : v(x >= 0 ? x % mod() : x % mod() + mod()) {}
  static constexpr MInt raw(const int x) {
    MInt x_;
    x_.v = x;
    return x_;
  }

  static int get_mod() { return mod(); }
  static void set_mod(const unsigned int divisor) { mod() = divisor; }

  static void init(const int x) {
    inv<true>(x);
    fact(x);
    fact_inv(x);
  }

  template <bool MEMOIZES = false>
  static MInt inv(const int n) {
    // assert(0 <= n && n < mod() && std::gcd(x, mod()) == 1);
    static std::vector<MInt> inverse{0, 1};
    const int prev = inverse.size();
    if (n < prev) return inverse[n];
    if constexpr (MEMOIZES) {
      // "n!" and "M" must be disjoint.
      inverse.resize(n + 1);
      for (int i = prev; i <= n; ++i) {
        inverse[i] = -inverse[mod() % i] * raw(mod() / i);
      }
      return inverse[n];
    }
    int u = 1, v = 0;
    for (unsigned int a = n, b = mod(); b;) {
      const unsigned int q = a / b;
      std::swap(a -= q * b, b);
      std::swap(u -= q * v, v);
    }
    return u;
  }

  static MInt fact(const int n) {
    static std::vector<MInt> factorial{1};
    if (const int prev = factorial.size(); n >= prev) {
      factorial.resize(n + 1);
      for (int i = prev; i <= n; ++i) {
        factorial[i] = factorial[i - 1] * i;
      }
    }
    return factorial[n];
  }

  static MInt fact_inv(const int n) {
    static std::vector<MInt> f_inv{1};
    if (const int prev = f_inv.size(); n >= prev) {
      f_inv.resize(n + 1);
      f_inv[n] = inv(fact(n).v);
      for (int i = n; i > prev; --i) {
        f_inv[i - 1] = f_inv[i] * i;
      }
    }
    return f_inv[n];
  }

  static MInt nCk(const int n, const int k) {
    if (n < 0 || n < k || k < 0) [[unlikely]] return MInt();
    return fact(n) * (n - k < k ? fact_inv(k) * fact_inv(n - k) :
                                  fact_inv(n - k) * fact_inv(k));
  }
  static MInt nPk(const int n, const int k) {
    return n < 0 || n < k || k < 0 ? MInt() : fact(n) * fact_inv(n - k);
  }
  static MInt nHk(const int n, const int k) {
    return n < 0 || k < 0 ? MInt() : (k == 0 ? 1 : nCk(n + k - 1, k));
  }

  static MInt large_nCk(long long n, const int k) {
    if (n < 0 || n < k || k < 0) [[unlikely]] return MInt();
    inv<true>(k);
    MInt res = 1;
    for (int i = 1; i <= k; ++i) {
      res *= inv(i) * n--;
    }
    return res;
  }

  MInt pow(long long exponent) const {
    MInt res = 1, tmp = *this;
    for (; exponent > 0; exponent >>= 1) {
      if (exponent & 1) res *= tmp;
      tmp *= tmp;
    }
    return res;
  }

  MInt& operator+=(const MInt& x) {
    if ((v += x.v) >= mod()) v -= mod();
    return *this;
  }
  MInt& operator-=(const MInt& x) {
    if ((v += mod() - x.v) >= mod()) v -= mod();
    return *this;
  }
  MInt& operator*=(const MInt& x) {
    v = (unsigned long long){v} * x.v % mod();
    return *this;
    }
  MInt& operator/=(const MInt& x) { return *this *= inv(x.v); }

  auto operator<=>(const MInt& x) const = default;

  MInt& operator++() {
    if (++v == mod()) [[unlikely]] v = 0;
    return *this;
  }
  MInt operator++(int) {
    const MInt res = *this;
    ++*this;
    return res;
  }
  MInt& operator--() {
    v = (v == 0 ? mod() - 1 : v - 1);
    return *this;
  }
  MInt operator--(int) {
    const MInt res = *this;
    --*this;
    return res;
  }

  MInt operator+() const { return *this; }
  MInt operator-() const { return raw(v ? mod() - v : 0); }

  MInt operator+(const MInt& x) const { return MInt(*this) += x; }
  MInt operator-(const MInt& x) const { return MInt(*this) -= x; }
  MInt operator*(const MInt& x) const { return MInt(*this) *= x; }
  MInt operator/(const MInt& x) const { return MInt(*this) /= x; }

  friend std::ostream& operator<<(std::ostream& os, const MInt& x) {
    return os << x.v;
  }
  friend std::istream& operator>>(std::istream& is, MInt& x) {
    long long v;
    is >> v;
    x = MInt(v);
    return is;
  }

 private:
  static unsigned int& mod() {
    static unsigned int divisor = 0;
    return divisor;
  }
};
#endif  // ARBITRARY_MODINT

}  // namespace emthrm


#line 10 "include/emthrm/graph/flow/matching/maximum_matching.hpp"

namespace emthrm {

int maximum_matching(const std::vector<std::vector<int>>& graph) {
  constexpr unsigned int P = 1000000007;
  using ModInt = MInt<P>;
  ModInt::set_mod(P);
  static std::mt19937_64 engine(std::random_device {} ());
  static std::uniform_int_distribution<> dist(1, P - 1);
  const int n = graph.size();
  Matrix<ModInt> tutte_matrix(n, n, 0);
  for (int i = 0; i < n; ++i) {
    for (const int j : graph[i]) {
      if (j > i) {
        const ModInt x = ModInt::raw(dist(engine));
        tutte_matrix[i][j] = x;
        tutte_matrix[j][i] = -x;
      }
    }
  }
  return gauss_jordan(&tutte_matrix, ModInt(0)) / 2;
}

}  // namespace emthrm


#line 12 "test/graph/flow/matching/maximum_matching.test.cpp"

int main() {
  int n, a, b;
  std::cin >> n >> a >> b;
  int ans = 0;
  std::vector<int> as, bs;
  while (n--) {
    int a_i, b_i;
    std::cin >> a_i >> b_i;
    const int x = std::abs(a_i - b_i);
    if (x <= a || (b <= x && x <= 2 * a)) {
      ++ans;
    } else {
      as.emplace_back(a_i);
      bs.emplace_back(b_i);
    }
  }
  n = as.size();
  if (n > 0) {
    std::vector<std::vector<int>> graph(n);
    for (int i = 0; i < n; ++i) {
      for (int j = i + 1; j < n; ++j) {
        const int x = std::abs((as[i] + as[j]) - (bs[i] + bs[j]));
        if (x <= a || (b <= x && x <= 2 * a)) {
          graph[i].emplace_back(j);
          graph[j].emplace_back(i);
        }
      }
    }
    ans += emthrm::maximum_matching(graph);
  }
  std::cout << ans << '\n';
  return 0;
}
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