proconlib
This documentation is automatically generated by competitive-verifier/competitive-verifier
tests/lowlink/ncc_without_vertex.test.cpp
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- Last update: 2025-06-21 22:00:23+09:00
- Problem: https://atcoder.jp/contests/abc334/tasks/abc334_g
Depends on
chmin function (tools/chmin.hpp)- Fixed point combinator (tools/fix.hpp)
- std::less by key (tools/less_by.hpp)
- Lowlink (tools/lowlink.hpp)
Code
// competitive-verifier: PROBLEM https://atcoder.jp/contests/abc334/tasks/abc334_g
// competitive-verifier: IGNORE
#include <iostream>
#include <string>
#include <vector>
#include "atcoder/modint.hpp"
#include "tools/lowlink.hpp"
using mint = atcoder::modint998244353;
int main() {
std::cin.tie(nullptr);
std::ios_base::sync_with_stdio(false);
int H, W;
std::cin >> H >> W;
std::vector<std::string> S(H);
for (auto&& S_i : S) std::cin >> S_i;
auto V = std::vector(H, std::vector<int>(W, -1));
int k = 0;
for (int i = 0; i < H; ++i) {
for (int j = 0; j < W; ++j) {
if (S[i][j] == '#') {
V[i][j] = k++;
}
}
}
tools::lowlink graph(k);
for (int i = 0; i < H; ++i) {
for (int j = 0; j < W; ++j) {
if (i + 1 < H && S[i][j] == '#' && S[i + 1][j] == '#') {
graph.add_edge(V[i][j], V[i + 1][j]);
}
if (j + 1 < W && S[i][j] == '#' && S[i][j + 1] == '#') {
graph.add_edge(V[i][j], V[i][j + 1]);
}
}
}
graph.build();
auto answer = mint::raw(0);
for (int v = 0; v < k; ++v) {
answer += mint::raw(graph.ncc_without_vertex(v));
}
answer /= mint::raw(k);
std::cout << answer.val() << '\n';
return 0;
}
#line 1 "tests/lowlink/ncc_without_vertex.test.cpp"
// competitive-verifier: PROBLEM https://atcoder.jp/contests/abc334/tasks/abc334_g
// competitive-verifier: IGNORE
#include <iostream>
#include <string>
#include <vector>
#line 1 "lib/ac-library/atcoder/modint.hpp"
#include <cassert>
#include <numeric>
#include <type_traits>
#ifdef _MSC_VER
#include <intrin.h>
#endif
#line 1 "lib/ac-library/atcoder/internal_math.hpp"
#include <utility>
#ifdef _MSC_VER
#include <intrin.h>
#endif
namespace atcoder {
namespace internal {
// @param m `1 <= m`
// @return x mod m
constexpr long long safe_mod(long long x, long long m) {
x %= m;
if (x < 0) x += m;
return x;
}
// Fast modular multiplication by barrett reduction
// Reference: https://en.wikipedia.org/wiki/Barrett_reduction
// NOTE: reconsider after Ice Lake
struct barrett {
unsigned int _m;
unsigned long long im;
// @param m `1 <= m`
explicit barrett(unsigned int m) : _m(m), im((unsigned long long)(-1) / m + 1) {}
// @return m
unsigned int umod() const { return _m; }
// @param a `0 <= a < m`
// @param b `0 <= b < m`
// @return `a * b % m`
unsigned int mul(unsigned int a, unsigned int b) const {
// [1] m = 1
// a = b = im = 0, so okay
// [2] m >= 2
// im = ceil(2^64 / m)
// -> im * m = 2^64 + r (0 <= r < m)
// let z = a*b = c*m + d (0 <= c, d < m)
// a*b * im = (c*m + d) * im = c*(im*m) + d*im = c*2^64 + c*r + d*im
// c*r + d*im < m * m + m * im < m * m + 2^64 + m <= 2^64 + m * (m + 1) < 2^64 * 2
// ((ab * im) >> 64) == c or c + 1
unsigned long long z = a;
z *= b;
#ifdef _MSC_VER
unsigned long long x;
_umul128(z, im, &x);
#else
unsigned long long x =
(unsigned long long)(((unsigned __int128)(z)*im) >> 64);
#endif
unsigned long long y = x * _m;
return (unsigned int)(z - y + (z < y ? _m : 0));
}
};
// @param n `0 <= n`
// @param m `1 <= m`
// @return `(x ** n) % m`
constexpr long long pow_mod_constexpr(long long x, long long n, int m) {
if (m == 1) return 0;
unsigned int _m = (unsigned int)(m);
unsigned long long r = 1;
unsigned long long y = safe_mod(x, m);
while (n) {
if (n & 1) r = (r * y) % _m;
y = (y * y) % _m;
n >>= 1;
}
return r;
}
// Reference:
// M. Forisek and J. Jancina,
// Fast Primality Testing for Integers That Fit into a Machine Word
// @param n `0 <= n`
constexpr bool is_prime_constexpr(int n) {
if (n <= 1) return false;
if (n == 2 || n == 7 || n == 61) return true;
if (n % 2 == 0) return false;
long long d = n - 1;
while (d % 2 == 0) d /= 2;
constexpr long long bases[3] = {2, 7, 61};
for (long long a : bases) {
long long t = d;
long long y = pow_mod_constexpr(a, t, n);
while (t != n - 1 && y != 1 && y != n - 1) {
y = y * y % n;
t <<= 1;
}
if (y != n - 1 && t % 2 == 0) {
return false;
}
}
return true;
}
template <int n> constexpr bool is_prime = is_prime_constexpr(n);
// @param b `1 <= b`
// @return pair(g, x) s.t. g = gcd(a, b), xa = g (mod b), 0 <= x < b/g
constexpr std::pair<long long, long long> inv_gcd(long long a, long long b) {
a = safe_mod(a, b);
if (a == 0) return {b, 0};
// Contracts:
// [1] s - m0 * a = 0 (mod b)
// [2] t - m1 * a = 0 (mod b)
// [3] s * |m1| + t * |m0| <= b
long long s = b, t = a;
long long m0 = 0, m1 = 1;
while (t) {
long long u = s / t;
s -= t * u;
m0 -= m1 * u; // |m1 * u| <= |m1| * s <= b
// [3]:
// (s - t * u) * |m1| + t * |m0 - m1 * u|
// <= s * |m1| - t * u * |m1| + t * (|m0| + |m1| * u)
// = s * |m1| + t * |m0| <= b
auto tmp = s;
s = t;
t = tmp;
tmp = m0;
m0 = m1;
m1 = tmp;
}
// by [3]: |m0| <= b/g
// by g != b: |m0| < b/g
if (m0 < 0) m0 += b / s;
return {s, m0};
}
// Compile time primitive root
// @param m must be prime
// @return primitive root (and minimum in now)
constexpr int primitive_root_constexpr(int m) {
if (m == 2) return 1;
if (m == 167772161) return 3;
if (m == 469762049) return 3;
if (m == 754974721) return 11;
if (m == 998244353) return 3;
int divs[20] = {};
divs[0] = 2;
int cnt = 1;
int x = (m - 1) / 2;
while (x % 2 == 0) x /= 2;
for (int i = 3; (long long)(i)*i <= x; i += 2) {
if (x % i == 0) {
divs[cnt++] = i;
while (x % i == 0) {
x /= i;
}
}
}
if (x > 1) {
divs[cnt++] = x;
}
for (int g = 2;; g++) {
bool ok = true;
for (int i = 0; i < cnt; i++) {
if (pow_mod_constexpr(g, (m - 1) / divs[i], m) == 1) {
ok = false;
break;
}
}
if (ok) return g;
}
}
template <int m> constexpr int primitive_root = primitive_root_constexpr(m);
// @param n `n < 2^32`
// @param m `1 <= m < 2^32`
// @return sum_{i=0}^{n-1} floor((ai + b) / m) (mod 2^64)
unsigned long long floor_sum_unsigned(unsigned long long n,
unsigned long long m,
unsigned long long a,
unsigned long long b) {
unsigned long long ans = 0;
while (true) {
if (a >= m) {
ans += n * (n - 1) / 2 * (a / m);
a %= m;
}
if (b >= m) {
ans += n * (b / m);
b %= m;
}
unsigned long long y_max = a * n + b;
if (y_max < m) break;
// y_max < m * (n + 1)
// floor(y_max / m) <= n
n = (unsigned long long)(y_max / m);
b = (unsigned long long)(y_max % m);
std::swap(m, a);
}
return ans;
}
} // namespace internal
} // namespace atcoder
#line 1 "lib/ac-library/atcoder/internal_type_traits.hpp"
#line 7 "lib/ac-library/atcoder/internal_type_traits.hpp"
namespace atcoder {
namespace internal {
#ifndef _MSC_VER
template <class T>
using is_signed_int128 =
typename std::conditional<std::is_same<T, __int128_t>::value ||
std::is_same<T, __int128>::value,
std::true_type,
std::false_type>::type;
template <class T>
using is_unsigned_int128 =
typename std::conditional<std::is_same<T, __uint128_t>::value ||
std::is_same<T, unsigned __int128>::value,
std::true_type,
std::false_type>::type;
template <class T>
using make_unsigned_int128 =
typename std::conditional<std::is_same<T, __int128_t>::value,
__uint128_t,
unsigned __int128>;
template <class T>
using is_integral = typename std::conditional<std::is_integral<T>::value ||
is_signed_int128<T>::value ||
is_unsigned_int128<T>::value,
std::true_type,
std::false_type>::type;
template <class T>
using is_signed_int = typename std::conditional<(is_integral<T>::value &&
std::is_signed<T>::value) ||
is_signed_int128<T>::value,
std::true_type,
std::false_type>::type;
template <class T>
using is_unsigned_int =
typename std::conditional<(is_integral<T>::value &&
std::is_unsigned<T>::value) ||
is_unsigned_int128<T>::value,
std::true_type,
std::false_type>::type;
template <class T>
using to_unsigned = typename std::conditional<
is_signed_int128<T>::value,
make_unsigned_int128<T>,
typename std::conditional<std::is_signed<T>::value,
std::make_unsigned<T>,
std::common_type<T>>::type>::type;
#else
template <class T> using is_integral = typename std::is_integral<T>;
template <class T>
using is_signed_int =
typename std::conditional<is_integral<T>::value && std::is_signed<T>::value,
std::true_type,
std::false_type>::type;
template <class T>
using is_unsigned_int =
typename std::conditional<is_integral<T>::value &&
std::is_unsigned<T>::value,
std::true_type,
std::false_type>::type;
template <class T>
using to_unsigned = typename std::conditional<is_signed_int<T>::value,
std::make_unsigned<T>,
std::common_type<T>>::type;
#endif
template <class T>
using is_signed_int_t = std::enable_if_t<is_signed_int<T>::value>;
template <class T>
using is_unsigned_int_t = std::enable_if_t<is_unsigned_int<T>::value>;
template <class T> using to_unsigned_t = typename to_unsigned<T>::type;
} // namespace internal
} // namespace atcoder
#line 14 "lib/ac-library/atcoder/modint.hpp"
namespace atcoder {
namespace internal {
struct modint_base {};
struct static_modint_base : modint_base {};
template <class T> using is_modint = std::is_base_of<modint_base, T>;
template <class T> using is_modint_t = std::enable_if_t<is_modint<T>::value>;
} // namespace internal
template <int m, std::enable_if_t<(1 <= m)>* = nullptr>
struct static_modint : internal::static_modint_base {
using mint = static_modint;
public:
static constexpr int mod() { return m; }
static mint raw(int v) {
mint x;
x._v = v;
return x;
}
static_modint() : _v(0) {}
template <class T, internal::is_signed_int_t<T>* = nullptr>
static_modint(T v) {
long long x = (long long)(v % (long long)(umod()));
if (x < 0) x += umod();
_v = (unsigned int)(x);
}
template <class T, internal::is_unsigned_int_t<T>* = nullptr>
static_modint(T v) {
_v = (unsigned int)(v % umod());
}
unsigned int val() const { return _v; }
mint& operator++() {
_v++;
if (_v == umod()) _v = 0;
return *this;
}
mint& operator--() {
if (_v == 0) _v = umod();
_v--;
return *this;
}
mint operator++(int) {
mint result = *this;
++*this;
return result;
}
mint operator--(int) {
mint result = *this;
--*this;
return result;
}
mint& operator+=(const mint& rhs) {
_v += rhs._v;
if (_v >= umod()) _v -= umod();
return *this;
}
mint& operator-=(const mint& rhs) {
_v -= rhs._v;
if (_v >= umod()) _v += umod();
return *this;
}
mint& operator*=(const mint& rhs) {
unsigned long long z = _v;
z *= rhs._v;
_v = (unsigned int)(z % umod());
return *this;
}
mint& operator/=(const mint& rhs) { return *this = *this * rhs.inv(); }
mint operator+() const { return *this; }
mint operator-() const { return mint() - *this; }
mint pow(long long n) const {
assert(0 <= n);
mint x = *this, r = 1;
while (n) {
if (n & 1) r *= x;
x *= x;
n >>= 1;
}
return r;
}
mint inv() const {
if (prime) {
assert(_v);
return pow(umod() - 2);
} else {
auto eg = internal::inv_gcd(_v, m);
assert(eg.first == 1);
return eg.second;
}
}
friend mint operator+(const mint& lhs, const mint& rhs) {
return mint(lhs) += rhs;
}
friend mint operator-(const mint& lhs, const mint& rhs) {
return mint(lhs) -= rhs;
}
friend mint operator*(const mint& lhs, const mint& rhs) {
return mint(lhs) *= rhs;
}
friend mint operator/(const mint& lhs, const mint& rhs) {
return mint(lhs) /= rhs;
}
friend bool operator==(const mint& lhs, const mint& rhs) {
return lhs._v == rhs._v;
}
friend bool operator!=(const mint& lhs, const mint& rhs) {
return lhs._v != rhs._v;
}
private:
unsigned int _v;
static constexpr unsigned int umod() { return m; }
static constexpr bool prime = internal::is_prime<m>;
};
template <int id> struct dynamic_modint : internal::modint_base {
using mint = dynamic_modint;
public:
static int mod() { return (int)(bt.umod()); }
static void set_mod(int m) {
assert(1 <= m);
bt = internal::barrett(m);
}
static mint raw(int v) {
mint x;
x._v = v;
return x;
}
dynamic_modint() : _v(0) {}
template <class T, internal::is_signed_int_t<T>* = nullptr>
dynamic_modint(T v) {
long long x = (long long)(v % (long long)(mod()));
if (x < 0) x += mod();
_v = (unsigned int)(x);
}
template <class T, internal::is_unsigned_int_t<T>* = nullptr>
dynamic_modint(T v) {
_v = (unsigned int)(v % mod());
}
unsigned int val() const { return _v; }
mint& operator++() {
_v++;
if (_v == umod()) _v = 0;
return *this;
}
mint& operator--() {
if (_v == 0) _v = umod();
_v--;
return *this;
}
mint operator++(int) {
mint result = *this;
++*this;
return result;
}
mint operator--(int) {
mint result = *this;
--*this;
return result;
}
mint& operator+=(const mint& rhs) {
_v += rhs._v;
if (_v >= umod()) _v -= umod();
return *this;
}
mint& operator-=(const mint& rhs) {
_v += mod() - rhs._v;
if (_v >= umod()) _v -= umod();
return *this;
}
mint& operator*=(const mint& rhs) {
_v = bt.mul(_v, rhs._v);
return *this;
}
mint& operator/=(const mint& rhs) { return *this = *this * rhs.inv(); }
mint operator+() const { return *this; }
mint operator-() const { return mint() - *this; }
mint pow(long long n) const {
assert(0 <= n);
mint x = *this, r = 1;
while (n) {
if (n & 1) r *= x;
x *= x;
n >>= 1;
}
return r;
}
mint inv() const {
auto eg = internal::inv_gcd(_v, mod());
assert(eg.first == 1);
return eg.second;
}
friend mint operator+(const mint& lhs, const mint& rhs) {
return mint(lhs) += rhs;
}
friend mint operator-(const mint& lhs, const mint& rhs) {
return mint(lhs) -= rhs;
}
friend mint operator*(const mint& lhs, const mint& rhs) {
return mint(lhs) *= rhs;
}
friend mint operator/(const mint& lhs, const mint& rhs) {
return mint(lhs) /= rhs;
}
friend bool operator==(const mint& lhs, const mint& rhs) {
return lhs._v == rhs._v;
}
friend bool operator!=(const mint& lhs, const mint& rhs) {
return lhs._v != rhs._v;
}
private:
unsigned int _v;
static internal::barrett bt;
static unsigned int umod() { return bt.umod(); }
};
template <int id> internal::barrett dynamic_modint<id>::bt(998244353);
using modint998244353 = static_modint<998244353>;
using modint1000000007 = static_modint<1000000007>;
using modint = dynamic_modint<-1>;
namespace internal {
template <class T>
using is_static_modint = std::is_base_of<internal::static_modint_base, T>;
template <class T>
using is_static_modint_t = std::enable_if_t<is_static_modint<T>::value>;
template <class> struct is_dynamic_modint : public std::false_type {};
template <int id>
struct is_dynamic_modint<dynamic_modint<id>> : public std::true_type {};
template <class T>
using is_dynamic_modint_t = std::enable_if_t<is_dynamic_modint<T>::value>;
} // namespace internal
} // namespace atcoder
#line 1 "tools/lowlink.hpp"
#include <algorithm>
#line 6 "tools/lowlink.hpp"
#include <cstddef>
#include <initializer_list>
#include <iterator>
#include <limits>
#include <stack>
#include <tuple>
#line 1 "tools/chmin.hpp"
#line 6 "tools/chmin.hpp"
namespace tools {
template <typename M, typename N>
bool chmin(M& lhs, const N& rhs) {
bool updated;
if constexpr (::std::is_integral_v<M> && ::std::is_integral_v<N>) {
updated = ::std::cmp_less(rhs, lhs);
} else {
updated = rhs < lhs;
}
if (updated) lhs = rhs;
return updated;
}
}
#line 1 "tools/fix.hpp"
#line 6 "tools/fix.hpp"
namespace tools {
template <typename F>
struct fix : F {
template <typename G>
fix(G&& g) : F({::std::forward<G>(g)}) {
}
template <typename... Args>
decltype(auto) operator()(Args&&... args) const {
return F::operator()(*this, ::std::forward<Args>(args)...);
}
};
template <typename F>
fix(F&&) -> fix<::std::decay_t<F>>;
}
#line 1 "tools/less_by.hpp"
namespace tools {
template <class F>
class less_by {
private:
F selector;
public:
less_by(const F& selector) : selector(selector) {
}
template <class T>
bool operator()(const T& x, const T& y) const {
return selector(x) < selector(y);
}
};
}
#line 17 "tools/lowlink.hpp"
namespace tools {
class lowlink {
public:
struct edge {
int from;
int to;
};
private:
::std::vector<edge> m_edges;
::std::vector<::std::vector<int>> m_graph;
bool m_built;
::std::vector<int> m_from;
::std::vector<int> m_ord;
::std::vector<int> m_low;
int m_ncc;
::std::vector<int> m_ncc_without_vertex;
public:
class neighbors_iterable {
private:
::tools::lowlink const *m_parent;
int m_v;
public:
class iterator {
private:
::tools::lowlink const *m_parent;
int m_v;
int m_i;
public:
using difference_type = ::std::ptrdiff_t;
using value_type = int;
using reference = const int&;
using pointer = const int*;
using iterator_category = ::std::input_iterator_tag;
iterator() = default;
iterator(::tools::lowlink const * const parent, const int v, const int i) : m_parent(parent), m_v(v), m_i(i) {
}
value_type operator*() const {
const auto& edge = this->m_parent->m_edges[this->m_parent->m_graph[this->m_v][this->m_i]];
return edge.from ^ edge.to ^ this->m_v;
}
iterator& operator++() {
++this->m_i;
return *this;
}
iterator operator++(int) {
const auto self = *this;
++*this;
return self;
}
friend bool operator==(const iterator& lhs, const iterator& rhs) {
assert(lhs.m_parent == rhs.m_parent);
assert(lhs.m_v == rhs.m_v);
return lhs.m_i == rhs.m_i;
}
friend bool operator!=(const iterator& lhs, const iterator& rhs) {
return !(lhs == rhs);
}
};
neighbors_iterable() = default;
neighbors_iterable(::tools::lowlink const * const parent, const int v) : m_parent(parent), m_v(v) {
}
iterator begin() const {
return iterator(this->m_parent, this->m_v, 0);
};
iterator end() const {
return iterator(this->m_parent, this->m_v, this->m_parent->m_graph[this->m_v].size());
}
};
class edges_iterable {
private:
::tools::lowlink const *m_parent;
int m_v;
public:
class iterator {
private:
::tools::lowlink const *m_parent;
int m_v;
int m_i;
public:
using difference_type = ::std::ptrdiff_t;
using value_type = edge;
using reference = const edge&;
using pointer = const edge*;
using iterator_category = ::std::input_iterator_tag;
iterator() = default;
iterator(::tools::lowlink const * const parent, const int v, const int i) : m_parent(parent), m_v(v), m_i(i) {
}
reference operator*() const {
return this->m_parent->m_edges[this->m_parent->m_graph[this->m_v][this->m_i]];
}
iterator& operator++() {
++this->m_i;
return *this;
}
iterator operator++(int) {
const auto self = *this;
++*this;
return self;
}
friend bool operator==(const iterator& lhs, const iterator& rhs) {
assert(lhs.m_parent == rhs.m_parent);
assert(lhs.m_v == rhs.m_v);
return lhs.m_i == rhs.m_i;
}
friend bool operator!=(const iterator& lhs, const iterator& rhs) {
return !(lhs == rhs);
}
};
edges_iterable() = default;
edges_iterable(::tools::lowlink const * const parent, const int v) : m_parent(parent), m_v(v) {
}
iterator begin() const {
return iterator(this->m_parent, this->m_v, 0);
};
iterator end() const {
return iterator(this->m_parent, this->m_v, this->m_parent->m_graph[this->m_v].size());
}
};
class vchildren_iterable {
private:
::tools::lowlink const *m_parent;
int m_v;
public:
class iterator {
private:
::tools::lowlink const *m_parent;
int m_v;
int m_i;
public:
using difference_type = ::std::ptrdiff_t;
using value_type = int;
using reference = const int&;
using pointer = const int*;
using iterator_category = ::std::input_iterator_tag;
iterator() = default;
iterator(::tools::lowlink const * const parent, const int v, const int i) : m_parent(parent), m_v(v), m_i(i) {
const auto& eids = this->m_parent->m_graph[this->m_v];
for (; this->m_i < eids.size() && [&]() {
const auto eid = eids[this->m_i];
const auto& edge = this->m_parent->m_edges[eid];
return this->m_parent->m_from[edge.from ^ edge.to ^ this->m_v] != eid;
}(); ++this->m_i);
}
value_type operator*() const {
const auto& edge = this->m_parent->m_edges[this->m_parent->m_graph[this->m_v][this->m_i]];
return edge.from ^ edge.to ^ this->m_v;
}
iterator& operator++() {
const auto& eids = this->m_parent->m_graph[this->m_v];
assert(this->m_i < eids.size());
for (++this->m_i; this->m_i < eids.size() && [&]() {
const auto eid = eids[this->m_i];
const auto& edge = this->m_parent->m_edges[eid];
return this->m_parent->m_from[edge.from ^ edge.to ^ this->m_v] != eid;
}(); ++this->m_i);
return *this;
}
iterator operator++(int) {
const auto self = *this;
++*this;
return self;
}
friend bool operator==(const iterator& lhs, const iterator& rhs) {
assert(lhs.m_parent == rhs.m_parent);
assert(lhs.m_v == rhs.m_v);
return lhs.m_i == rhs.m_i;
}
friend bool operator!=(const iterator& lhs, const iterator& rhs) {
return !(lhs == rhs);
}
};
vchildren_iterable() = default;
vchildren_iterable(::tools::lowlink const * const parent, const int v) : m_parent(parent), m_v(v) {
}
iterator begin() const {
return iterator(this->m_parent, this->m_v, 0);
};
iterator end() const {
return iterator(this->m_parent, this->m_v, this->m_parent->m_graph[this->m_v].size());
}
};
class echildren_iterable {
private:
::tools::lowlink const *m_parent;
int m_v;
public:
class iterator {
private:
::tools::lowlink const *m_parent;
int m_v;
int m_i;
public:
using difference_type = ::std::ptrdiff_t;
using value_type = edge;
using reference = const edge&;
using pointer = const edge*;
using iterator_category = ::std::input_iterator_tag;
iterator() = default;
iterator(::tools::lowlink const * const parent, const int v, const int i) : m_parent(parent), m_v(v), m_i(i) {
const auto& eids = this->m_parent->m_graph[this->m_v];
for (; this->m_i < eids.size() && [&]() {
const auto eid = eids[this->m_i];
const auto& edge = this->m_parent->m_edges[eid];
return this->m_parent->m_from[edge.from ^ edge.to ^ this->m_v] != eid;
}(); ++this->m_i);
}
reference operator*() const {
return this->m_parent->m_edges[this->m_parent->m_graph[this->m_v][this->m_i]];
}
iterator& operator++() {
const auto& eids = this->m_parent->m_graph[this->m_v];
assert(this->m_i < eids.size());
for (++this->m_i; this->m_i < eids.size() && [&]() {
const auto eid = eids[this->m_i];
const auto& edge = this->m_parent->m_edges[eid];
return this->m_parent->m_from[edge.from ^ edge.to ^ this->m_v] != eid;
}(); ++this->m_i);
return *this;
}
iterator operator++(int) {
const auto self = *this;
++*this;
return self;
}
friend bool operator==(const iterator& lhs, const iterator& rhs) {
assert(lhs.m_parent == rhs.m_parent);
assert(lhs.m_v == rhs.m_v);
return lhs.m_i == rhs.m_i;
}
friend bool operator!=(const iterator& lhs, const iterator& rhs) {
return !(lhs == rhs);
}
};
echildren_iterable() = default;
echildren_iterable(::tools::lowlink const * const parent, const int v) : m_parent(parent), m_v(v) {
}
iterator begin() const {
return iterator(this->m_parent, this->m_v, 0);
};
iterator end() const {
return iterator(this->m_parent, this->m_v, this->m_parent->m_graph[this->m_v].size());
}
};
lowlink() = default;
explicit lowlink(const int n) : m_graph(n), m_built(false) {
}
int size() const {
return this->m_graph.size();
}
int add_edge(int u, int v) {
assert(!this->m_built);
assert(0 <= u && u < this->size());
assert(0 <= v && v < this->size());
::std::tie(u, v) = ::std::minmax({u, v});
this->m_edges.push_back(edge{u, v});
this->m_graph[u].push_back(this->m_edges.size() - 1);
this->m_graph[v].push_back(this->m_edges.size() - 1);
return this->m_edges.size() - 1;
}
const edge& get_edge(const int k) const {
assert(0 <= k && k < this->m_edges.size());
return this->m_edges[k];
}
const ::std::vector<edge>& edges() const {
return this->m_edges;
}
neighbors_iterable neighbors(const int v) const {
assert(0 <= v && v < this->size());
return neighbors_iterable(this, v);
}
edges_iterable edges(const int v) const {
assert(0 <= v && v < this->size());
return edges_iterable(this, v);
}
void build() {
assert(!this->m_built);
this->m_built = true;
const auto N_A = -1;
this->m_from.assign(this->size(), N_A);
this->m_ord.assign(this->size(), N_A);
this->m_low.assign(this->size(), N_A);
this->m_ncc = 0;
for (int r = 0; r < this->size(); ++r) {
if (this->m_ord[r] != N_A) continue;
++this->m_ncc;
int next_ord = 0;
::std::stack<::std::pair<int, int>> stack;
stack.emplace(r, N_A);
stack.emplace(r, N_A - 1);
while (!stack.empty()) {
const auto [v, from] = stack.top();
stack.pop();
if (from != N_A) {
if (this->m_ord[v] != N_A) continue;
this->m_from[v] = from;
this->m_ord[v] = next_ord++;
for (const auto eid : this->m_graph[v]) {
const auto& edge = this->m_edges[eid];
const auto u = edge.from ^ edge.to ^ v;
if (this->m_ord[u] != N_A) continue;
stack.emplace(u, N_A);
stack.emplace(u, eid);
}
} else {
if (this->m_low[v] != N_A) continue;
this->m_low[v] = this->m_ord[v];
for (const auto eid : this->m_graph[v]) {
const auto& edge = this->m_edges[eid];
const auto u = edge.from ^ edge.to ^ v;
if (this->m_ord[u] < this->m_ord[v] && eid != this->m_from[v]) {
::tools::chmin(this->m_low[v], this->m_ord[u]);
} else if (this->m_ord[u] > this->m_ord[v] && eid == this->m_from[u]) {
::tools::chmin(this->m_low[v], this->m_low[u]);
}
}
}
}
this->m_from[r] = N_A;
}
this->m_ncc_without_vertex.assign(this->size(), this->m_ncc);
for (int v = 0; v < this->size(); ++v) {
if (this->m_ord[v] == 0) {
this->m_ncc_without_vertex[v] += ::std::distance(this->echildren(v).begin(), this->echildren(v).end());
--this->m_ncc_without_vertex[v];
} else {
for (const auto& edge : this->echildren(v)) {
const auto u = edge.from ^ edge.to ^ v;
if (this->m_ord[v] <= this->m_low[u]) {
++this->m_ncc_without_vertex[v];
}
}
}
}
}
int vparent(const int v) const {
assert(this->m_built);
assert(0 <= v && v < this->size());
assert(this->m_ord[v] > 0);
const auto& edge = this->m_edges[this->m_from[v]];
return edge.from ^ edge.to ^ v;
}
const edge& eparent(const int v) const {
assert(this->m_built);
assert(0 <= v && v < this->size());
assert(this->m_ord[v] > 0);
return this->m_edges[this->m_from[v]];
}
vchildren_iterable vchildren(const int v) const {
assert(this->m_built);
assert(0 <= v && v < this->size());
return vchildren_iterable(this, v);
}
echildren_iterable echildren(const int v) const {
assert(this->m_built);
assert(0 <= v && v < this->size());
return echildren_iterable(this, v);
}
int ord(const int v) const {
assert(this->m_built);
assert(0 <= v && v < this->size());
return this->m_ord[v];
}
int low(const int v) const {
assert(this->m_built);
assert(0 <= v && v < this->size());
return this->m_low[v];
}
int ncc() const {
assert(this->m_built);
return this->m_ncc;
}
int ncc_without_vertex(const int v) const {
assert(this->m_built);
assert(0 <= v && v < this->size());
return this->m_ncc_without_vertex[v];
}
bool is_articulation_point(const int v) const {
assert(this->m_built);
assert(0 <= v && v < this->size());
return this->m_ncc_without_vertex[v] > this->m_ncc;
}
bool is_bridge(const int k) const {
assert(this->m_built);
assert(0 <= k && k < this->m_edges.size());
const auto [u, v] = ::std::minmax({this->m_edges[k].from, this->m_edges[k].to}, ::tools::less_by([&](const auto w) { return this->m_ord[w]; }));
return this->m_ord[u] < this->m_low[v];
}
::std::vector<::std::vector<int>> biconnected_components() const {
assert(this->m_built);
::std::vector<::std::vector<int>> groups;
for (int r = 0; r < this->size(); ++r) {
if (this->ord(r) == 0) {
if (this->m_ncc_without_vertex[r] < this->m_ncc) {
groups.emplace_back(::std::initializer_list<int>{r});
} else {
::tools::fix([&](auto&& dfs, const auto g, const auto v) -> void {
for (const auto u : this->vchildren(v)) {
if (this->ord(v) <= this->low(u)) {
groups.emplace_back(::std::initializer_list<int>{v, u});
dfs(groups.size() - 1, u);
} else {
groups[g].push_back(u);
dfs(g, u);
}
}
})(-1, r);
}
}
}
return groups;
}
};
}
#line 9 "tests/lowlink/ncc_without_vertex.test.cpp"
using mint = atcoder::modint998244353;
int main() {
std::cin.tie(nullptr);
std::ios_base::sync_with_stdio(false);
int H, W;
std::cin >> H >> W;
std::vector<std::string> S(H);
for (auto&& S_i : S) std::cin >> S_i;
auto V = std::vector(H, std::vector<int>(W, -1));
int k = 0;
for (int i = 0; i < H; ++i) {
for (int j = 0; j < W; ++j) {
if (S[i][j] == '#') {
V[i][j] = k++;
}
}
}
tools::lowlink graph(k);
for (int i = 0; i < H; ++i) {
for (int j = 0; j < W; ++j) {
if (i + 1 < H && S[i][j] == '#' && S[i + 1][j] == '#') {
graph.add_edge(V[i][j], V[i + 1][j]);
}
if (j + 1 < W && S[i][j] == '#' && S[i][j + 1] == '#') {
graph.add_edge(V[i][j], V[i][j + 1]);
}
}
}
graph.build();
auto answer = mint::raw(0);
for (int v = 0; v < k; ++v) {
answer += mint::raw(graph.ncc_without_vertex(v));
}
answer /= mint::raw(k);
std::cout << answer.val() << '\n';
return 0;
}