結果

問題 No.1507 Road Blocked
ユーザー tokusakurai
提出日時 2021-05-14 22:23:11
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 81 ms / 2,000 ms
コード長 3,918 bytes
コンパイル時間 2,225 ms
コンパイル使用メモリ 203,264 KB
最終ジャッジ日時 2025-01-21 11:28:43
ジャッジサーバーID
(参考情報)
judge3 / 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 #
プレゼンテーションモードにする

#include <bits/stdc++.h>
using namespace std;
#define rep(i, n) for(int i = 0; i < n; i++)
#define rep2(i, x, n) for(int i = x; i <= n; i++)
#define rep3(i, x, n) for(int i = x; i >= n; i--)
#define each(e, v) for(auto &e: v)
#define pb push_back
#define eb emplace_back
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define sz(x) (int)x.size()
using ll = long long;
using pii = pair<int, int>;
using pil = pair<int, ll>;
using pli = pair<ll, int>;
using pll = pair<ll, ll>;
//const int MOD = 1000000007;
const int MOD = 998244353;
const int inf = (1<<30)-1;
const ll INF = (1LL<<60)-1;
template<typename T> bool chmax(T &x, const T &y) {return (x < y)? (x = y, true) : false;};
template<typename T> bool chmin(T &x, const T &y) {return (x > y)? (x = y, true) : false;};
struct io_setup{
io_setup(){
ios_base::sync_with_stdio(false);
cin.tie(NULL);
cout << fixed << setprecision(15);
}
} io_setup;
template<int mod>
struct Mod_Int{
int x;
Mod_Int() : x(0) {}
Mod_Int(long long y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
Mod_Int &operator += (const Mod_Int &p){
if((x += p.x) >= mod) x -= mod;
return *this;
}
Mod_Int &operator -= (const Mod_Int &p){
if((x += mod - p.x) >= mod) x -= mod;
return *this;
}
Mod_Int &operator *= (const Mod_Int &p){
x = (int) (1LL * x * p.x % mod);
return *this;
}
Mod_Int &operator /= (const Mod_Int &p){
*this *= p.inverse();
return *this;
}
Mod_Int &operator ++ () {return *this += Mod_Int(1);}
Mod_Int operator ++ (int){
Mod_Int tmp = *this;
++*this;
return tmp;
}
Mod_Int &operator -- () {return *this -= Mod_Int(1);}
Mod_Int operator -- (int){
Mod_Int tmp = *this;
--*this;
return tmp;
}
Mod_Int operator - () const {return Mod_Int(-x);}
Mod_Int operator + (const Mod_Int &p) const {return Mod_Int(*this) += p;}
Mod_Int operator - (const Mod_Int &p) const {return Mod_Int(*this) -= p;}
Mod_Int operator * (const Mod_Int &p) const {return Mod_Int(*this) *= p;}
Mod_Int operator / (const Mod_Int &p) const {return Mod_Int(*this) /= p;}
bool operator == (const Mod_Int &p) const {return x == p.x;}
bool operator != (const Mod_Int &p) const {return x != p.x;}
Mod_Int inverse() const{
assert(*this != Mod_Int(0));
return pow(mod-2);
}
Mod_Int pow(long long k) const{
Mod_Int now = *this, ret = 1;
for(; k > 0; k >>= 1, now *= now){
if(k&1) ret *= now;
}
return ret;
}
friend ostream &operator << (ostream &os, const Mod_Int &p){
return os << p.x;
}
friend istream &operator >> (istream &is, Mod_Int &p){
long long a;
is >> a;
p = Mod_Int<mod>(a);
return is;
}
};
using mint = Mod_Int<MOD>;
mint S = 0;
mint M;
template<bool directed = false>
struct Graph{
struct edge{
int to, id;
edge(int to, int id) : to(to), id(id) {}
};
vector<vector<edge>> es;
const int n;
int m;
vector<mint> si;
Graph(int n) : es(n), n(n), m(0), si(n) {}
void add_edge(int from, int to){
es[from].emplace_back(to, m);
if(!directed) es[to].emplace_back(from, m);
m++;
}
mint dfs(int now, int pre = -1){
si[now] = 1;
each(e, es[now]){
if(e.to == pre) continue;
mint K = dfs(e.to, now);
S += K*(M-K);
si[now] += K;
}
return si[now];
}
};
int main(){
int N; cin >> N;
M = mint(N);
Graph G(N);
rep(i, N-1){
int u, v; cin >> u >> v; u--, v--;
G.add_edge(u, v);
}
G.dfs(0);
mint R = M*(M-1)*(M-1);
//cout << S << ' ' << R << '\n';
cout << (R-S*2)/R << '\n';
}
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