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// @brief Counting Spanning Trees (Undirected)
#define PROBLEM "https://judge.yosupo.jp/problem/counting_spanning_tree_undirected"
#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("tune=native")
#include "cp-algo/linalg/matrix.hpp"
#include <bits/stdc++.h>
using namespace std;
using namespace cp_algo::math;
using namespace cp_algo::linalg;
const int64_t mod = 998244353;
using base = modint<mod>;
void solve() {
int n, m;
cin >> n >> m;
matrix<base> a(n);
for(int i = 0; i < m; i++) {
int u, v;
cin >> u >> v;
a[u][v] -= 1;
a[v][u] -= 1;
a[v][v] += 1;
a[u][u] += 1;
}
for(int i = 0; i < n; i++) {
a[0][i] = a[i][0] = 0;
}
a[0][0] = 1;
cout << a.det() << "\n";
}
signed main() {
//freopen("input.txt", "r", stdin);
ios::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
while(t--) {
solve();
}
}
#line 1 "verify/linalg/spanning_undirected.test.cpp"
// @brief Counting Spanning Trees (Undirected)
#define PROBLEM "https://judge.yosupo.jp/problem/counting_spanning_tree_undirected"
#pragma GCC optimize("Ofast,unroll-loops")
#pragma GCC target("tune=native")
#line 1 "cp-algo/linalg/matrix.hpp"
#line 1 "cp-algo/random/rng.hpp"
#include <chrono>
#include <random>
namespace cp_algo::random {
uint64_t rng() {
static std::mt19937_64 rng(
std::chrono::steady_clock::now().time_since_epoch().count()
);
return rng();
}
}
#line 1 "cp-algo/math/common.hpp"
#include <functional>
#include <cstdint>
namespace cp_algo::math {
#ifdef CP_ALGO_MAXN
const int maxn = CP_ALGO_MAXN;
#else
const int maxn = 1 << 19;
#endif
const int magic = 64; // threshold for sizes to run the naive algo
auto bpow(auto const& x, auto n, auto const& one, auto op) {
if(n == 0) {
return one;
} else {
auto t = bpow(x, n / 2, one, op);
t = op(t, t);
if(n % 2) {
t = op(t, x);
}
return t;
}
}
auto bpow(auto x, auto n, auto ans) {
return bpow(x, n, ans, std::multiplies{});
}
template<typename T>
T bpow(T const& x, auto n) {
return bpow(x, n, T(1));
}
}
#line 1 "cp-algo/linalg/vector.hpp"
#line 1 "cp-algo/number_theory/modint.hpp"
#line 4 "cp-algo/number_theory/modint.hpp"
#include <iostream>
#include <cassert>
namespace cp_algo::math {
inline constexpr auto inv2(auto x) {
assert(x % 2);
std::make_unsigned_t<decltype(x)> y = 1;
while(y * x != 1) {
y *= 2 - x * y;
}
return y;
}
template<typename modint, typename _Int>
struct modint_base {
using Int = _Int;
using UInt = std::make_unsigned_t<Int>;
static constexpr size_t bits = sizeof(Int) * 8;
using Int2 = std::conditional_t<bits <= 32, int64_t, __int128_t>;
using UInt2 = std::conditional_t<bits <= 32, uint64_t, __uint128_t>;
static Int mod() {
return modint::mod();
}
static UInt imod() {
return modint::imod();
}
static UInt2 pw128() {
return modint::pw128();
}
static UInt m_reduce(UInt2 ab) {
if(mod() % 2 == 0) [[unlikely]] {
return UInt(ab % mod());
} else {
UInt2 m = (UInt)ab * imod();
return UInt((ab + m * mod()) >> bits);
}
}
static UInt m_transform(UInt a) {
if(mod() % 2 == 0) [[unlikely]] {
return a;
} else {
return m_reduce(a * pw128());
}
}
modint_base(): r(0) {}
modint_base(Int2 rr): r(UInt(rr % mod())) {
r = std::min(r, r + mod());
r = m_transform(r);
}
modint inv() const {
return bpow(to_modint(), mod() - 2);
}
modint operator - () const {
modint neg;
neg.r = std::min(-r, 2 * mod() - r);
return neg;
}
modint& operator /= (const modint &t) {
return to_modint() *= t.inv();
}
modint& operator *= (const modint &t) {
r = m_reduce((UInt2)r * t.r);
return to_modint();
}
modint& operator += (const modint &t) {
r += t.r; r = std::min(r, r - 2 * mod());
return to_modint();
}
modint& operator -= (const modint &t) {
r -= t.r; r = std::min(r, r + 2 * mod());
return to_modint();
}
modint operator + (const modint &t) const {return modint(to_modint()) += t;}
modint operator - (const modint &t) const {return modint(to_modint()) -= t;}
modint operator * (const modint &t) const {return modint(to_modint()) *= t;}
modint operator / (const modint &t) const {return modint(to_modint()) /= t;}
// Why <=> doesn't work?..
auto operator == (const modint_base &t) const {return getr() == t.getr();}
auto operator != (const modint_base &t) const {return getr() != t.getr();}
auto operator <= (const modint_base &t) const {return getr() <= t.getr();}
auto operator >= (const modint_base &t) const {return getr() >= t.getr();}
auto operator < (const modint_base &t) const {return getr() < t.getr();}
auto operator > (const modint_base &t) const {return getr() > t.getr();}
Int rem() const {
UInt R = getr();
return 2 * R > (UInt)mod() ? R - mod() : R;
}
// Only use if you really know what you're doing!
UInt modmod() const {return (UInt)8 * mod() * mod();};
void add_unsafe(UInt t) {r += t;}
void pseudonormalize() {r = std::min(r, r - modmod());}
modint const& normalize() {
if(r >= (UInt)mod()) {
r %= mod();
}
return to_modint();
}
void setr(UInt rr) {r = m_transform(rr);}
UInt getr() const {
UInt res = m_reduce(r);
return std::min(res, res - mod());
}
void setr_direct(UInt rr) {r = rr;}
UInt getr_direct() const {return r;}
private:
UInt r;
modint& to_modint() {return static_cast<modint&>(*this);}
modint const& to_modint() const {return static_cast<modint const&>(*this);}
};
template<typename modint>
concept modint_type = std::is_base_of_v<modint_base<modint, typename modint::Int>, modint>;
template<modint_type modint>
std::istream& operator >> (std::istream &in, modint &x) {
typename modint::UInt r;
auto &res = in >> r;
x.setr(r);
return res;
}
template<modint_type modint>
std::ostream& operator << (std::ostream &out, modint const& x) {
return out << x.getr();
}
template<auto m>
struct modint: modint_base<modint<m>, decltype(m)> {
using Base = modint_base<modint<m>, decltype(m)>;
using Base::Base;
static constexpr Base::UInt im = m % 2 ? inv2(-m) : 0;
static constexpr Base::UInt r2 = (typename Base::UInt2)(-1) % m + 1;
static constexpr Base::Int mod() {return m;}
static constexpr Base::UInt imod() {return im;}
static constexpr Base::UInt2 pw128() {return r2;}
};
template<typename Int = int64_t>
struct dynamic_modint: modint_base<dynamic_modint<Int>, Int> {
using Base = modint_base<dynamic_modint<Int>, Int>;
using Base::Base;
static Int mod() {return m;}
static Base::UInt imod() {return im;}
static Base::UInt2 pw128() {return r2;}
static void switch_mod(Int nm) {
m = nm;
im = m % 2 ? inv2(-m) : 0;
r2 = static_cast<Base::UInt>(static_cast<Base::UInt2>(-1) % m + 1);
}
// Wrapper for temp switching
auto static with_mod(Int tmp, auto callback) {
struct scoped {
Int prev = mod();
~scoped() {switch_mod(prev);}
} _;
switch_mod(tmp);
return callback();
}
private:
static thread_local Int m;
static thread_local Base::UInt im, r2;
};
template<typename Int>
Int thread_local dynamic_modint<Int>::m = 1;
template<typename Int>
dynamic_modint<Int>::Base::UInt thread_local dynamic_modint<Int>::im = -1;
template<typename Int>
dynamic_modint<Int>::Base::UInt thread_local dynamic_modint<Int>::r2 = 0;
}
#line 6 "cp-algo/linalg/vector.hpp"
#include <algorithm>
#include <valarray>
#line 9 "cp-algo/linalg/vector.hpp"
#include <iterator>
#line 11 "cp-algo/linalg/vector.hpp"
namespace cp_algo::linalg {
template<class vec, typename base>
struct valarray_base: std::valarray<base> {
using Base = std::valarray<base>;
using Base::Base;
valarray_base(base const& t): Base(t, 1) {}
auto begin() {return std::begin(to_valarray());}
auto begin() const {return std::begin(to_valarray());}
auto end() {return std::end(to_valarray());}
auto end() const {return std::end(to_valarray());}
bool operator == (vec const& t) const {return std::ranges::equal(*this, t);}
bool operator != (vec const& t) const {return !(*this == t);}
vec operator-() const {return Base::operator-();}
static vec from_range(auto const& R) {
vec res(std::ranges::distance(R));
std::ranges::copy(R, res.begin());
return res;
}
Base& to_valarray() {return static_cast<Base&>(*this);}
Base const& to_valarray() const {return static_cast<Base const&>(*this);}
};
template<class vec, typename base>
vec operator+(valarray_base<vec, base> const& a, valarray_base<vec, base> const& b) {
return a.to_valarray() + b.to_valarray();
}
template<class vec, typename base>
vec operator-(valarray_base<vec, base> const& a, valarray_base<vec, base> const& b) {
return a.to_valarray() - b.to_valarray();
}
template<class vec, typename base>
struct vec_base: valarray_base<vec, base> {
using Base = valarray_base<vec, base>;
using Base::Base;
static vec ei(size_t n, size_t i) {
vec res(n);
res[i] = 1;
return res;
}
virtual void add_scaled(vec const& b, base scale, size_t i = 0) {
if(scale != base(0)) {
for(; i < size(*this); i++) {
(*this)[i] += scale * b[i];
}
}
}
virtual vec const& normalize() {
return static_cast<vec&>(*this);
}
virtual base normalize(size_t i) {
return (*this)[i];
}
void read() {
for(auto &it: *this) {
std::cin >> it;
}
}
void print() const {
std::ranges::copy(*this, std::ostream_iterator<base>(std::cout, " "));
std::cout << "\n";
}
static vec random(size_t n) {
vec res(n);
std::ranges::generate(res, random::rng);
return res;
}
// Concatenate vectors
vec operator |(vec const& t) const {
vec res(size(*this) + size(t));
res[std::slice(0, size(*this), 1)] = *this;
res[std::slice(size(*this), size(t), 1)] = t;
return res;
}
// Generally, vec shouldn't be modified
// after its pivot index is set
std::pair<size_t, base> find_pivot() {
if(pivot == size_t(-1)) {
pivot = 0;
while(pivot < size(*this) && normalize(pivot) == base(0)) {
pivot++;
}
if(pivot < size(*this)) {
pivot_inv = base(1) / (*this)[pivot];
}
}
return {pivot, pivot_inv};
}
void reduce_by(vec &t) {
auto [pivot, pinv] = t.find_pivot();
if(pivot < size(*this)) {
add_scaled(t, -normalize(pivot) * pinv, pivot);
}
}
private:
size_t pivot = -1;
base pivot_inv;
};
template<typename base>
struct vec: vec_base<vec<base>, base> {
using Base = vec_base<vec<base>, base>;
using Base::Base;
};
template<math::modint_type base>
struct vec<base>: vec_base<vec<base>, base> {
using Base = vec_base<vec<base>, base>;
using Base::Base;
void add_scaled(vec const& b, base scale, size_t i = 0) override {
static_assert(base::bits >= 64, "Only wide modint types for linalg");
uint64_t scaler = scale.getr();
if(scale != base(0)) {
for(; i < size(*this); i++) {
(*this)[i].add_unsafe(scaler * b[i].getr_direct());
}
if(++counter == 4) {
for(auto &it: *this) {
it.pseudonormalize();
}
counter = 0;
}
}
}
vec const& normalize() override {
for(auto &it: *this) {
it.normalize();
}
return *this;
}
base normalize(size_t i) override {
return (*this)[i].normalize();
}
private:
size_t counter = 0;
};
}
#line 7 "cp-algo/linalg/matrix.hpp"
#include <optional>
#line 9 "cp-algo/linalg/matrix.hpp"
#include <vector>
#include <array>
namespace cp_algo::linalg {
enum gauss_mode {normal, reverse};
template<typename base_t>
struct matrix: valarray_base<matrix<base_t>, vec<base_t>> {
using base = base_t;
using Base = valarray_base<matrix<base>, vec<base>>;
using Base::Base;
matrix(size_t n): Base(vec<base>(n), n) {}
matrix(size_t n, size_t m): Base(vec<base>(m), n) {}
size_t n() const {return size(*this);}
size_t m() const {return n() ? size(row(0)) : 0;}
auto dim() const {return std::array{n(), m()};}
auto& row(size_t i) {return (*this)[i];}
auto const& row(size_t i) const {return (*this)[i];}
matrix& operator *=(base t) {for(auto &it: *this) it *= t; return *this;}
matrix operator *(base t) const {return matrix(*this) *= t;}
matrix& operator /=(base t) {return *this *= base(1) / t;}
matrix operator /(base t) const {return matrix(*this) /= t;}
// Make sure the result is matrix, not Base
matrix& operator *=(matrix const& t) {return *this = *this * t;}
void read() {
for(auto &it: *this) {
it.read();
}
}
void print() const {
for(auto const& it: *this) {
it.print();
}
}
static matrix block_diagonal(std::vector<matrix> const& blocks) {
size_t n = 0;
for(auto &it: blocks) {
assert(it.n() == it.m());
n += it.n();
}
matrix res(n);
n = 0;
for(auto &it: blocks) {
for(size_t i = 0; i < it.n(); i++) {
res[n + i][std::slice(n, it.n(), 1)] = it[i];
}
n += it.n();
}
return res;
}
static matrix random(size_t n, size_t m) {
matrix res(n, m);
std::ranges::generate(res, std::bind(vec<base>::random, m));
return res;
}
static matrix random(size_t n) {
return random(n, n);
}
static matrix eye(size_t n) {
matrix res(n);
for(size_t i = 0; i < n; i++) {
res[i][i] = 1;
}
return res;
}
// Concatenate matrices
matrix operator |(matrix const& b) const {
assert(n() == b.n());
matrix res(n(), m()+b.m());
for(size_t i = 0; i < n(); i++) {
res[i] = row(i) | b[i];
}
return res;
}
matrix submatrix(auto slicex, auto slicey) const {
matrix res = (*this)[slicex];
for(auto &row: res) {
row = vec<base>(row[slicey]);
}
return res;
}
matrix T() const {
matrix res(m(), n());
for(size_t i = 0; i < n(); i++) {
for(size_t j = 0; j < m(); j++) {
res[j][i] = row(i)[j];
}
}
return res;
}
matrix operator *(matrix const& b) const {
assert(m() == b.n());
matrix res(n(), b.m());
for(size_t i = 0; i < n(); i++) {
for(size_t j = 0; j < m(); j++) {
res[i].add_scaled(b[j], row(i)[j]);
}
}
return res.normalize();
}
vec<base> apply(vec<base> const& x) const {
return (matrix(x) * *this)[0];
}
matrix pow(uint64_t k) const {
assert(n() == m());
return bpow(*this, k, eye(n()));
}
matrix& normalize() {
for(auto &it: *this) {
it.normalize();
}
return *this;
}
template<gauss_mode mode = normal>
void eliminate(size_t i, size_t k) {
auto kinv = base(1) / row(i).normalize()[k];
for(size_t j = (mode == normal) * i; j < n(); j++) {
if(j != i) {
row(j).add_scaled(row(i), -row(j).normalize(k) * kinv);
}
}
}
template<gauss_mode mode = normal>
void eliminate(size_t i) {
row(i).normalize();
for(size_t j = (mode == normal) * i; j < n(); j++) {
if(j != i) {
row(j).reduce_by(row(i));
}
}
}
template<gauss_mode mode = normal>
matrix& gauss() {
for(size_t i = 0; i < n(); i++) {
eliminate<mode>(i);
}
return normalize();
}
template<gauss_mode mode = normal>
auto echelonize(size_t lim) {
return gauss<mode>().sort_classify(lim);
}
template<gauss_mode mode = normal>
auto echelonize() {
return echelonize<mode>(m());
}
size_t rank() const {
if(n() > m()) {
return T().rank();
}
return size(matrix(*this).echelonize()[0]);
}
base det() const {
assert(n() == m());
matrix b = *this;
b.echelonize();
base res = 1;
for(size_t i = 0; i < n(); i++) {
res *= b[i][i];
}
return res;
}
std::pair<base, matrix> inv() const {
assert(n() == m());
matrix b = *this | eye(n());
if(size(b.echelonize<reverse>(n())[0]) < n()) {
return {0, {}};
}
base det = 1;
for(size_t i = 0; i < n(); i++) {
det *= b[i][i];
b[i] *= base(1) / b[i][i];
}
return {det, b.submatrix(std::slice(0, n(), 1), std::slice(n(), n(), 1))};
}
// Can also just run gauss on T() | eye(m)
// but it would be slower :(
auto kernel() const {
auto A = *this;
auto [pivots, free] = A.template echelonize<reverse>();
matrix sols(size(free), m());
for(size_t j = 0; j < size(pivots); j++) {
base scale = base(1) / A[j][pivots[j]];
for(size_t i = 0; i < size(free); i++) {
sols[i][pivots[j]] = A[j][free[i]] * scale;
}
}
for(size_t i = 0; i < size(free); i++) {
sols[i][free[i]] = -1;
}
return sols;
}
// [solution, basis], transposed
std::optional<std::array<matrix, 2>> solve(matrix t) const {
matrix sols = (*this | t).kernel();
if(sols.n() < t.m() || sols.submatrix(
std::slice(sols.n() - t.m(), t.m(), 1),
std::slice(m(), t.m(), 1)
) != -eye(t.m())) {
return std::nullopt;
} else {
return std::array{
sols.submatrix(std::slice(sols.n() - t.m(), t.m(), 1),
std::slice(0, m(), 1)),
sols.submatrix(std::slice(0, sols.n() - t.m(), 1),
std::slice(0, m(), 1))
};
}
}
// To be called after a gaussian elimination run
// Sorts rows by pivots and classifies
// variables into pivots and free
auto sort_classify(size_t lim) {
size_t rk = 0;
std::vector<size_t> free, pivots;
for(size_t j = 0; j < lim; j++) {
for(size_t i = rk + 1; i < n() && row(rk)[j] == base(0); i++) {
if(row(i)[j] != base(0)) {
std::swap(row(i), row(rk));
row(rk) = -row(rk);
}
}
if(rk < n() && row(rk)[j] != base(0)) {
pivots.push_back(j);
rk++;
} else {
free.push_back(j);
}
}
return std::array{pivots, free};
}
};
template<typename base_t>
auto operator *(base_t t, matrix<base_t> const& A) {return A * t;}
}
#line 6 "verify/linalg/spanning_undirected.test.cpp"
#include <bits/stdc++.h>
using namespace std;
using namespace cp_algo::math;
using namespace cp_algo::linalg;
const int64_t mod = 998244353;
using base = modint<mod>;
void solve() {
int n, m;
cin >> n >> m;
matrix<base> a(n);
for(int i = 0; i < m; i++) {
int u, v;
cin >> u >> v;
a[u][v] -= 1;
a[v][u] -= 1;
a[v][v] += 1;
a[u][u] += 1;
}
for(int i = 0; i < n; i++) {
a[0][i] = a[i][0] = 0;
}
a[0][0] = 1;
cout << a.det() << "\n";
}
signed main() {
//freopen("input.txt", "r", stdin);
ios::sync_with_stdio(0);
cin.tie(0);
int t = 1;
// cin >> t;
while(t--) {
solve();
}
}
Env | Name | Status | Elapsed | Memory |
---|---|---|---|---|
g++ | example_00 | AC | 5 ms | 4 MB |
g++ | example_01 | AC | 4 ms | 4 MB |
g++ | example_02 | AC | 4 ms | 4 MB |
g++ | example_03 | AC | 4 ms | 4 MB |
g++ | max_00 | AC | 79 ms | 8 MB |
g++ | max_01 | AC | 80 ms | 8 MB |
g++ | max_02 | AC | 78 ms | 8 MB |
g++ | random_00 | AC | 51 ms | 4 MB |
g++ | random_01 | AC | 52 ms | 4 MB |
g++ | random_02 | AC | 40 ms | 4 MB |
g++ | random_03 | AC | 9 ms | 4 MB |
g++ | random_04 | AC | 14 ms | 4 MB |
g++ | small_00 | AC | 4 ms | 4 MB |
g++ | small_01 | AC | 4 ms | 4 MB |
g++ | small_02 | AC | 4 ms | 4 MB |
g++ | small_03 | AC | 4 ms | 4 MB |
g++ | small_04 | AC | 4 ms | 4 MB |
g++ | small_05 | AC | 4 ms | 4 MB |
g++ | small_06 | AC | 4 ms | 4 MB |
g++ | small_07 | AC | 4 ms | 4 MB |
g++ | small_08 | AC | 4 ms | 4 MB |
g++ | small_09 | AC | 4 ms | 4 MB |