結果

問題 No.1507 Road Blocked
コンテスト
ユーザー GRMN
提出日時 2021-06-20 22:13:40
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
WA  
実行時間 -
コード長 4,501 bytes
コンパイル時間 4,307 ms
コンパイル使用メモリ 253,228 KB
最終ジャッジ日時 2025-01-22 10:52:42
ジャッジサーバーID
（参考情報） 		judge3 / judge2
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 * 1 WA * 29
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>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
#define rep(i,n) for (int i = 0; i < (n); i++)
#define REP(i,a,b) for(int i=(a);i<(b);i++)
#define all(v) begin(v),end(v)
#define rall(v) rbegin(v),rend(v)
#define fi first
#define se second
#define re0 return 0
template<typename A, typename B> inline bool chmax(A &a, B b) { if (a<b) { a=b; return 1; } return 0; }
template<typename A, typename B> inline bool chmin(A &a, B b) { if (a>b) { a=b; return 1; } return 0; }
using ll = long long;
using pii = pair<int, int>;
using pll = pair<ll, ll>;
using tup = tuple<ll, ll, ll>;
using cp = complex<double>;
constexpr ll inf = 2e9;
constexpr ll llinf = 9e18;
constexpr ll MOD = 998244353;
//constexpr ll MOD = 1000000007;
const double pai = acos(-1);

/**
 * @brief https://tkmst201.github.io/Library/Mathematics/ModInt.hpp
 */
template<int M>
struct ModInt {
    static_assert(M > 0);
    
    using value_type = int;
    using calc_type = std::int_fast64_t;
    
private:
    value_type val_;
    
public:
    constexpr ModInt(calc_type val = 0) : val_(val % M + (val >= 0 ? 0 : M)) {}
    constexpr value_type val() const noexcept { return val_; }
    constexpr static decltype(M) mod() noexcept { return M; }
    
    explicit constexpr operator bool() const noexcept { return val_; }
    constexpr bool operator !() const noexcept { return !static_cast<bool>(*this); }
    constexpr ModInt operator +() const noexcept { return *this; }
    constexpr ModInt operator -() const noexcept { return ModInt(val_ == 0 ? 0 : M - val_); }
    constexpr ModInt operator ++(int) noexcept { ModInt res = *this; ++*this; return res; }
    constexpr ModInt operator --(int) noexcept { ModInt res = *this; --*this; return res; }
    constexpr ModInt & operator ++() noexcept { val_ = val_ + 1 == M ? 0 : val_ + 1; return *this; }
    constexpr ModInt & operator --() noexcept { val_ = val_ == 0 ? M - 1 : val_ - 1; return *this; }
    constexpr ModInt & operator +=(const ModInt & rhs) noexcept { val_ += val_ < M - rhs.val_ ? rhs.val_ : rhs.val_ - M; return *this; }
    constexpr ModInt & operator -=(const ModInt & rhs) noexcept { val_ += val_ >= rhs.val_ ? -rhs.val_ : M - rhs.val_; return *this; }
    constexpr ModInt & operator *=(const ModInt & rhs) noexcept { val_ = static_cast<calc_type>(val_) * rhs.val_ % M; return *this; }
    constexpr ModInt & operator /=(const ModInt & rhs) noexcept { return *this *= rhs.inv(); }
    friend constexpr ModInt operator +(const ModInt & lhs, const ModInt & rhs) noexcept { return ModInt(lhs) += rhs; }
    friend constexpr ModInt operator -(const ModInt & lhs, const ModInt & rhs) noexcept { return ModInt(lhs) -= rhs; }
    friend constexpr ModInt operator *(const ModInt & lhs, const ModInt & rhs) noexcept { return ModInt(lhs) *= rhs; }
    friend constexpr ModInt operator /(const ModInt & lhs, const ModInt & rhs) noexcept { return ModInt(lhs) /= rhs; }
    friend constexpr bool operator ==(const ModInt & lhs, const ModInt & rhs) noexcept { return lhs.val_ == rhs.val_; }
    friend constexpr bool operator !=(const ModInt & lhs, const ModInt & rhs) noexcept { return !(lhs == rhs); }
    friend std::ostream & operator <<(std::ostream & os, const ModInt & rhs) { return os << rhs.val_; }
    friend std::istream & operator >>(std::istream & is, ModInt & rhs) { calc_type x; is >> x; rhs = ModInt(x); return is; }
    
    constexpr ModInt pow(calc_type n) const noexcept {
        ModInt res = 1, x = val_;
        if (n < 0) { x = x.inv(); n = -n; }
        while (n) { if (n & 1) res *= x; x *= x; n >>= 1; }
        return res;
    }
    
    constexpr ModInt inv() const noexcept {
        value_type a = val_, a1 = 1, b = M, b1 = 0;
        while (b > 0) {
            const value_type q = a / b;
            value_type tmp = a - q * b; a = b; b = tmp;
            tmp = a1 - q * b1; a1 = b1; b1 = tmp;
        }
        assert(a == 1);
        if (a1 < 0) a1 += M;
        return a1;
    }
};
using mint = ModInt<MOD>;

mint ans=0;
vector<vector<int>> g;
ll n;
ll cnt=0;

void dfs(int v,int p=-1){
    cnt++;
    for(int u:g[v]){
        if(u==p)continue;
        dfs(u,v);
    }
    cnt--;
    if(cnt!=0)ans+=cnt*(cnt-1)/2+(n-cnt)*(n-cnt-1)/2;
}

int main() {
    //cout<<fixed<<setprecision(15);
    cin>>n;
    g.resize(n);
    rep(i,n-1){
        int a,b;cin>>a>>b;
        a--;b--;
        g[a].push_back(b);
        g[b].push_back(a);
    }
    dfs(0);
    ans/=(n-1)*n*(n-1)/2;
    cout<<ans<<endl;
}
0