結果

問題 No.1507 Road Blocked
コンテスト
ユーザー そすうぽよ
提出日時 2021-05-14 22:25:16
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 113 ms / 2,000 ms
コード長 5,885 bytes
コンパイル時間 2,215 ms
コンパイル使用メモリ 199,368 KB
最終ジャッジ日時 2025-01-21 11:31:49
ジャッジサーバーID
（参考情報） 		judge2 / judge5
このコードへのチャレンジ
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ファイルパターン 結果
sample AC * 3
other AC * 30
権限があれば一括ダウンロードができます

ソースコード

diff # 

#include <bits/stdc++.h>
#include <variant>

#define rep2(i,k,n) for(i64 i=(i64)(k);i<(i64)(n);i++)
#define rep(i,n) rep2(i,0,n)
#define all(x) begin(x),end(x)
#ifdef ENV_LOCAL
#define dump if (1) cerr
#else
#define dump if (0) cerr
#endif

using namespace std;
using namespace std::string_literals;

using i32 = int32_t;
using i64 = int64_t;
using f64 = double;
using f80 = long double;
using vi32 = vector<i32>;
using vi64 = vector<i64>;

/*
 * harudake::modint
 *
 * Copyright (c) 2021 prime number
 *
 * This software is released under the MIT license.
 * see https://opensource.org/licenses/MIT
 *
 */
namespace harudake {

template <typename base_t, base_t MOD>
class static_modint;

using modint_1000000007 = static_modint<uint64_t, 1'000'000'007>;
using modint_998244353 = static_modint<uint64_t, 998'244'353>;

template <typename base_t, base_t MOD>
static_modint<base_t, MOD> add(const static_modint<base_t, MOD> lhs, const static_modint<base_t, MOD> rhs) {
  base_t tmp = lhs.val + rhs.val;
  if (tmp >= MOD) tmp -= MOD;
  return static_modint<base_t, MOD>::make_raw(tmp);
}

template <typename base_t, base_t MOD>
static_modint<base_t, MOD> sub(const static_modint<base_t, MOD> lhs, const static_modint<base_t, MOD> rhs) {
  base_t tmp = lhs.val + MOD - rhs.val;
  if (tmp >= MOD) tmp -= MOD;
  return static_modint<base_t, MOD>::make_raw(tmp);
}

template <typename base_t, base_t MOD>
static_modint<base_t, MOD> mul(const static_modint<base_t, MOD> lhs, const static_modint<base_t, MOD> rhs) {
  base_t tmp = lhs.val * rhs.val;
  tmp %= MOD;
  return static_modint<base_t, MOD>::make_raw(tmp);
}

// data types must be signed integer
inline int64_t inv (const int64_t a, const int64_t p) {
  return (a == 1 ? 1 : (1 - p * inv(p%a, a)) / a + p);
};

template <typename base_t, base_t MOD>
static_modint<base_t, MOD> div(const static_modint<base_t, MOD> lhs, const static_modint<base_t, MOD> rhs) {
  base_t tmp = lhs.val * inv(rhs.val, MOD);
  tmp %= MOD;
  return static_modint<base_t, MOD>::make_raw(tmp);
}

template <typename base_t, base_t MOD>
static_modint<base_t, MOD> pow(const static_modint<base_t, MOD> base, const uint64_t index) {
  if (index == 0) return static_modint<base_t, MOD> { 1 };
  if (index % 2 == 1) {
    return pow(base, index - 1) * base;
  } else {
    auto half = pow(base, index / 2);
    return half * half;
  }
}

template <typename base_t, base_t MOD>
class static_modint {
  using modint = static_modint;
 public:
  static constexpr base_t mod = MOD;
  static_modint() : val(0) {}
  static_modint(const base_t x) : val(x % MOD) {}
  static_modint(const modint&) = default;
  modint& operator=(const modint&) = default;
  modint& operator=(const base_t x) {
    val = x % MOD;
    return *this;
  }
  modint operator-() const { return val == 0 ? 0 : MOD - val; }
  explicit operator base_t() const { return val; }
  base_t get() const { return val; }
  constexpr base_t get_mod() const { return mod; }
  static modint make_raw(const base_t raw) {
    modint res;
    res.val = raw;
    return res;
  }
 private:
  friend modint add<base_t, MOD>(const modint, const modint);
  friend modint sub<base_t, MOD>(const modint, const modint);
  friend modint mul<base_t, MOD>(const modint, const modint);
  friend modint div<base_t, MOD>(const modint, const modint);
  base_t val;
};

template <typename base_t, base_t MOD>
static_modint<base_t, MOD> operator+(const static_modint<base_t, MOD> lhs, const static_modint<base_t, MOD> rhs) {
  return add(lhs, rhs);
}
template <typename base_t, base_t MOD>
static_modint<base_t, MOD> operator-(const static_modint<base_t, MOD> lhs, const static_modint<base_t, MOD> rhs) {
  return sub(lhs, rhs);
}
template <typename base_t, base_t MOD>
static_modint<base_t, MOD> operator*(const static_modint<base_t, MOD> lhs, const static_modint<base_t, MOD> rhs) {
  return mul(lhs, rhs);
}
template <typename base_t, base_t MOD>
static_modint<base_t, MOD> operator/(const static_modint<base_t, MOD> lhs, const static_modint<base_t, MOD> rhs) {
  return div(lhs, rhs);
}
template <typename base_t, base_t MOD>
static_modint<base_t, MOD> operator^(const static_modint<base_t, MOD> lhs, const uint64_t rhs) {
  return pow(lhs, rhs);
}

template <typename base_t, base_t MOD>
static_modint<base_t, MOD>& operator+=(static_modint<base_t, MOD>& lhs, const static_modint<base_t, MOD> rhs) {
  return lhs = lhs + rhs;
}
template <typename base_t, base_t MOD>
static_modint<base_t, MOD>& operator-=(static_modint<base_t, MOD>& lhs, const static_modint<base_t, MOD> rhs) {
  return lhs = lhs - rhs;
}
template <typename base_t, base_t MOD>
static_modint<base_t, MOD>& operator*=(static_modint<base_t, MOD>& lhs, const static_modint<base_t, MOD> rhs) {
  return lhs = lhs * rhs;
}
template <typename base_t, base_t MOD>
static_modint<base_t, MOD>& operator/=(static_modint<base_t, MOD>& lhs, const static_modint<base_t, MOD> rhs) {
  return lhs = lhs / rhs;
}
template <typename base_t, base_t MOD>
static_modint<base_t, MOD>& operator^=(static_modint<base_t, MOD>& lhs, const uint64_t rhs) {
  return lhs = lhs ^ rhs;
}

} // namespace harudake

using namespace harudake;
using modint = modint_998244353;

pair<i32, modint> dfs(const vector<vi32>& g, i32 n, i32 i, i32 p = -1) {
  i32 sz = 1;
  modint ans(0);
  for (auto&& to : g[i]) {
    if (to == p) continue;
    auto [csz, cval] = dfs(g, n, to, i);
    ans += cval;
    sz += csz;
  }
  if (sz < n) {
    modint mn(n);
    modint mk(sz);
    ans += (mk*(mk-modint(1)) + (mn-mk)*(mn-mk-modint(1))) / (mn * (mn - modint(1)));
  }
  return make_pair(sz, ans);
}

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);
  i64 n;
  cin>>n;
  vector<vi32> g(n);
  rep(i,n-1) {
    i32 u,v;
    cin>>u>>v;
    --u;--v;
    g[u].push_back(v);
    g[v].push_back(u);
  }
  auto [sz, ans] = dfs(g, n, 0);
  ans /= modint(n-1);
  cout<<ans.get()<<endl;
  return 0;
}
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