結果

問題 No.1507 Road Blocked
コンテスト
ユーザー stoq
提出日時 2021-05-14 22:31:03
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 93 ms / 2,000 ms
コード長 9,192 bytes
コンパイル時間 2,670 ms
コンパイル使用メモリ 215,508 KB
最終ジャッジ日時 2025-01-21 11:37:20
ジャッジサーバーID
（参考情報） 		judge2 / judge1
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 # 

#define MOD_TYPE 2

#pragma region Macros

#include <bits/stdc++.h>
using namespace std;

#if 0
#include <boost/multiprecision/cpp_int.hpp>
#include <boost/multiprecision/cpp_dec_float.hpp>
using Int = boost::multiprecision::cpp_int;
using lld = boost::multiprecision::cpp_dec_float_100;
#endif
#if 1
#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#endif
using ll = long long int;
using ld = long double;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using pld = pair<ld, ld>;
template <typename Q_type>
using smaller_queue = priority_queue<Q_type, vector<Q_type>, greater<Q_type>>;

constexpr ll MOD = (MOD_TYPE == 1 ? (ll)(1e9 + 7) : 998244353);
constexpr int INF = (int)1e9 + 10;
constexpr ll LINF = (ll)4e18;
constexpr ld PI = acos(-1.0);
constexpr ld EPS = 1e-7;
constexpr int Dx[] = {0, 0, -1, 1, -1, 1, -1, 1, 0};
constexpr int Dy[] = {1, -1, 0, 0, -1, -1, 1, 1, 0};

#define REP(i, m, n) for (ll i = m; i < (ll)(n); ++i)
#define rep(i, n) REP(i, 0, n)
#define REPI(i, m, n) for (int i = m; i < (int)(n); ++i)
#define repi(i, n) REPI(i, 0, n)
#define MP make_pair
#define MT make_tuple
#define YES(n) cout << ((n) ? "YES" : "NO") << "\n"
#define Yes(n) cout << ((n) ? "Yes" : "No") << "\n"
#define possible(n) cout << ((n) ? "possible" : "impossible") << "\n"
#define Possible(n) cout << ((n) ? "Possible" : "Impossible") << "\n"
#define all(v) v.begin(), v.end()
#define NP(v) next_permutation(all(v))
#define dbg(x) cerr << #x << ":" << x << "\n";

struct io_init
{
  io_init()
  {
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << setprecision(30) << setiosflags(ios::fixed);
  };
} io_init;
template <typename T>
inline bool chmin(T &a, T b)
{
  if (a > b)
  {
    a = b;
    return true;
  }
  return false;
}
template <typename T>
inline bool chmax(T &a, T b)
{
  if (a < b)
  {
    a = b;
    return true;
  }
  return false;
}
inline ll CEIL(ll a, ll b)
{
  return (a + b - 1) / b;
}
template <typename A, size_t N, typename T>
inline void Fill(A (&array)[N], const T &val)
{
  fill((T *)array, (T *)(array + N), val);
}
template <typename T, typename U>
constexpr istream &operator>>(istream &is, pair<T, U> &p) noexcept
{
  is >> p.first >> p.second;
  return is;
}
template <typename T, typename U>
constexpr ostream &operator<<(ostream &os, pair<T, U> &p) noexcept
{
  os << p.first << " " << p.second;
  return os;
}
#pragma endregion

// --------------------------------------

#pragma region mint
template <int MOD>
struct Fp
{
  long long val;

  constexpr Fp(long long v = 0) noexcept : val(v % MOD)
  {
    if (val < 0)
      v += MOD;
  }

  constexpr int getmod()
  {
    return MOD;
  }

  constexpr Fp operator-() const noexcept
  {
    return val ? MOD - val : 0;
  }

  constexpr Fp operator+(const Fp &r) const noexcept
  {
    return Fp(*this) += r;
  }

  constexpr Fp operator-(const Fp &r) const noexcept
  {
    return Fp(*this) -= r;
  }

  constexpr Fp operator*(const Fp &r) const noexcept
  {
    return Fp(*this) *= r;
  }

  constexpr Fp operator/(const Fp &r) const noexcept
  {
    return Fp(*this) /= r;
  }

  constexpr Fp &operator+=(const Fp &r) noexcept
  {
    val += r.val;
    if (val >= MOD)
      val -= MOD;
    return *this;
  }

  constexpr Fp &operator-=(const Fp &r) noexcept
  {
    val -= r.val;
    if (val < 0)
      val += MOD;
    return *this;
  }

  constexpr Fp &operator*=(const Fp &r) noexcept
  {
    val = val * r.val % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }

  constexpr Fp &operator/=(const Fp &r) noexcept
  {
    long long a = r.val, b = MOD, u = 1, v = 0;
    while (b)
    {
      long long t = a / b;
      a -= t * b;
      swap(a, b);
      u -= t * v;
      swap(u, v);
    }
    val = val * u % MOD;
    if (val < 0)
      val += MOD;
    return *this;
  }

  constexpr bool operator==(const Fp &r) const noexcept
  {
    return this->val == r.val;
  }

  constexpr bool operator!=(const Fp &r) const noexcept
  {
    return this->val != r.val;
  }

  friend constexpr ostream &operator<<(ostream &os, const Fp<MOD> &x) noexcept
  {
    return os << x.val;
  }

  friend constexpr istream &operator>>(istream &is, Fp<MOD> &x) noexcept
  {
    return is >> x.val;
  }
};

Fp<MOD> modpow(const Fp<MOD> &a, long long n) noexcept
{
  if (n == 0)
    return 1;
  auto t = modpow(a, n / 2);
  t = t * t;
  if (n & 1)
    t = t * a;
  return t;
}

using mint = Fp<MOD>;

template <class T>
struct BiCoef
{
  vector<T> fact_, inv_, finv_;

  constexpr BiCoef()
  {
  }

  constexpr BiCoef(int n) noexcept : fact_(n, 1), inv_(n, 1), finv_(n, 1)
  {
    init(n);
  }

  constexpr void init(int n) noexcept
  {
    fact_.assign(n, 1), inv_.assign(n, 1), finv_.assign(n, 1);
    int MOD = fact_[0].getmod();
    for (int i = 2; i < n; i++)
    {
      fact_[i] = fact_[i - 1] * i;
      inv_[i] = -inv_[MOD % i] * (MOD / i);
      finv_[i] = finv_[i - 1] * inv_[i];
    }
  }

  constexpr T C(ll n, ll k) const noexcept
  {
    if (n < k || n < 0 || k < 0)
      return 0;
    return fact_[n] * finv_[k] * finv_[n - k];
  }

  constexpr T P(ll n, ll k) const noexcept
  {
    return C(n, k) * fact_[k];
  }

  constexpr T H(ll n, ll k) const noexcept
  {
    return C(n + k - 1, k);
  }

  constexpr T Ch1(ll n, ll k) const noexcept
  {
    if (n < 0 || k < 0)
      return 0;
    T res = 0;
    for (int i = 0; i < n; i++)
      res += C(n, i) * modpow(n - i, k) * (i & 1 ? -1 : 1);
    return res;
  }

  constexpr T fact(ll n) const noexcept
  {
    if (n < 0)
      return 0;
    return fact_[n];
  }

  constexpr T inv(ll n) const noexcept
  {
    if (n < 0)
      return 0;
    return inv_[n];
  }

  constexpr T finv(ll n) const noexcept
  {
    if (n < 0)
      return 0;
    return finv_[n];
  }
};

BiCoef<mint> bc(200010);
#pragma endregion

template <typename T>
struct Tree
{
  int V;
  using P = pair<int, T>;
  vector<vector<P>> E;
  vector<int> par, depth, in, out;
  vector<T> dist;
  vector<vector<int>> par_double;

  Tree(int V) : V(V)
  {
    E.resize(V);
    depth.resize(V);
    dist.resize(V);
    in.resize(V);
    out.resize(V);
  }

  void read(int index = 1, bool ini = true)
  {
    int a, b;
    for (int i = 0; i < V - 1; i++)
    {
      cin >> a >> b, a -= index, b -= index;
      E[a].push_back({b, 1});
      E[b].push_back({a, 1});
    }
    if (ini)
      init();
  }

  void add_edge(int a, int b, T w = 1)
  {
    E[a].push_back({b, w});
    E[b].push_back({a, w});
  }

  void dfs(int v, int d, T w, int &i)
  {
    in[v] = i++;
    depth[v] = d;
    dist[v] = w;
    for (auto [c, di] : E[v])
    {
      if (par[v] == c)
        continue;
      par[c] = v;
      dfs(c, d + 1, w + di, i);
    }
    out[v] = i;
  }

  inline int sub(int v) { return out[v] - in[v]; }

  void init(int root = 0)
  {
    calculated = false;
    par.assign(V, -1);
    int i = 0;
    dfs(root, 0, 0, i);
  }

  bool calculated;
  void calc_double()
  {
    par_double.assign(V, vector<int>(25));
    for (int i = 0; i < V; i++)
      par_double[i][0] = par[i];

    for (int k = 0; k < 24; k++)
    {
      for (int i = 0; i < V; i++)
      {
        if (par_double[i][k] == -1)
          par_double[i][k + 1] = -1;
        else
          par_double[i][k + 1] = par_double[par_double[i][k]][k];
      }
    }
  }

  int getLCA(int a, int b)
  {
    if (!calculated)
      calc_double(), calculated = true;

    if (a == b)
      return a;
    if (depth[a] < depth[b])
      swap(a, b);
    for (int k = 24; k >= 0; k--)
    {
      if (par_double[a][k] != -1 && depth[par_double[a][k]] >= depth[b])
        a = par_double[a][k];
    }
    if (a == b)
      return a;
    for (int k = 24; k >= 0; k--)
    {
      if (par_double[a][k] != -1 && par_double[a][k] != par_double[b][k])
      {
        a = par_double[a][k];
        b = par_double[b][k];
      }
    }
    return par_double[a][0];
  }

  int length(int a, int b) { return depth[a] + depth[b] - 2 * depth[getLCA(a, b)]; }

  T distance(int a, int b) { return dist[a] + dist[b] - 2 * dist[getLCA(a, b)]; }

  T diameter(int &a, int &b)
  {
    T Max(-1), d;
    for (int i = 0; i < V; i++)
    {
      d = distance(0, i);
      if (Max < d)
        Max = d, a = i;
    }
    for (int i = 0; i < V; i++)
    {
      d = distance(a, i);
      if (Max < d)
        Max = d, b = i;
    }
    return Max;
  }

  T diameter()
  {
    int a, b;
    return diameter(a, b);
  }

  int unweighted_diameter(int &a, int &b)
  {
    int Max = 1, d;
    for (int i = 0; i < V; i++)
    {
      d = length(0, i);
      if (Max < d)
        Max = d, a = i;
    }
    for (int i = 0; i < V; i++)
    {
      d = length(a, i);
      if (Max < d)
        Max = d, b = i;
    }
    return Max;
  }

  int unweighted_diameter()
  {
    int a, b;
    return unweighted_diameter(a, b);
  }
};

void solve()
{
  ll n;
  cin >> n;
  Tree<int> tr(n);
  tr.read();
  tr.init();
  mint sum = 0;
  rep(a, n)
  {
    for (auto [b, tmp] : tr.E[a])
    {
      if (tr.par[a] == b)
        continue;
      int t = tr.sub(b);
      sum += bc.C(t, 2);
      t = -t + n;
      sum += bc.C(t, 2);
    }
  }
  sum /= bc.C(n, 2) * (n - 1);
  cout << sum << "\n";
}

int main()
{
  solve();
}
0