C++ Library for Competitive Programming
/*
* @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;
}