#1168855 (C++17) No.3346 Tree to DAG

• 問題: No.3346 Tree to DAG
• ユーザー: akua
• 提出日時: 2026-06-11 17:18:18
• 言語: C++17 (gcc 15.2.0 + boost 1.89.0)
• 結果: AC
• 実行時間: 160 ms / 2,000 ms
• コード長: 8,037 bytes
• コンパイル時間: 5,380 ms
• コンパイル使用メモリ: 283,684 KB
• 実行使用メモリ: 24,064 KB
• 最終ジャッジ日時: 2026-06-11 17:18:27
• 合計ジャッジ時間: 8,433 ms
• ジャッジサーバーID （参考情報）: judge2_1 / judge1_0

ファイルパターン	結果
sample	AC * 2
other	AC * 39

ソースコード

# pragma GCC target("avx2")
# pragma GCC optimize("O3")
# pragma GCC optimize("unroll-loops")
#include<atcoder/all>

#include <iostream> // cout, endl, cin
#include <string> // string, to_string, stoi
#include <vector> // vector
#include <algorithm> // min, max, swap, sort, reverse, lower_bound, upper_bound
#include <utility> // pair, make_pair
#include <tuple> // tuple, make_tuple
#include <cstdint> // int64_t, int*_t
#include <cstdio> // printf
#include <map> // map
#include <queue> // queue, priority_queue
#include <set> // set
#include <stack> // stack
#include <deque> // deque #include <unordered_map> // unordered_map #include <unordered_set> // unordered_set #include <bitset> // bitset
#include <cctype> // isupper, islower, isdigit, toupper, tolower
#include <math.h>
#include <iomanip>
#include <functional>
#include<unordered_map>
#include <random>
#include<bitset>
#include<cassert>
#include<chrono>
using namespace std;  
using namespace atcoder;
#define rep(i, n) for (int i = 0; i < (int)(n); i++)
#define repi(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define endl '\n'
#define all(x) (x).begin(),(x).end()
#define arr(x) (x).rbegin(),(x).rend()
typedef long long ll;
typedef unsigned long long ull;
const ll inf=4e18;  
using graph = vector<vector<int> > ;
using vi=vector<int>;
using P= pair<ll,ll>;  
using pii=pair<int,int>;
using pll=pair<ll,ll>;
using vvi=vector<vi>;
using vvvi=vector<vvi>;
using vll=vector<ll>; 
using vvll=vector<vll>;
using vvvll=vector<vvll>;
using vp=vector<P>;
using vvp=vector<vp>;
using vvvp=vector<vvp>;
using vd=vector<double>;
using vvd =vector<vd>;
//using vs=vector<string>;
//string T="ABCDEFGHIJKLMNOPQRSTUVWXYZ";
//string S="abcdefghijklmnopqrstuvwxyz";
//g++ main.cpp -std=c++17 -I .  
//cout <<setprecision(20);
//cout << fixed << setprecision(10);
//cin.tie(0); ios::sync_with_stdio(false);

const double PI = acos(-1);
int vx[]={0,1,0,-1,-1,1,1,-1},vy[]={1,0,-1,0,1,1,-1,-1};
void putsYes(bool f){cout << (f?"Yes":"No") << endl;}
void putsYES(bool f){cout << (f?"YES":"NO") << endl;}
void putsFirst(bool f){cout << (f?"First":"Second") << endl;}
void debug(int test){cout << "TEST" << " " << test << endl;}
ll pow_pow(ll x,ll n,ll mod){
    if(n==0) return 1; 
    x%=mod;
    ll res=pow_pow(x*x%mod,n/2,mod);
    if(n&1)res=res*x%mod;
    return res;
}
ll gcdll(ll x,ll y){
    if(y==0)return x;
    return gcdll(y,x%y);
}
ll INFF=1000100100100100100;
ll lcmll(ll x,ll y){
    ll X=(x/gcdll(x,y)),Y=y;
    if(X<=INFF/Y)return X*Y;
    else return INFF;
}
template<class T> bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    else return false;
}
template<class T> bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    else return false;
}
struct edge{
  int to; ll cost;int id;
  edge(int to,ll cost,int id) : to(to),cost(cost),id(id) {}
};
using ve=vector<edge>;
using vve=vector<ve>;
int mod=998244353;
using mint=modint998244353;
using vm=vector<mint>;
using vvm=vector<vm>;
using vvvm=vector<vvm>;
constexpr int MAX = 10;
ll fact[MAX],finv[MAX],invv[MAX];
void initcomb(){
  fact[0]=fact[1]=1;
  finv[0]=finv[1]=1;
  invv[1]=1;
  for(int i=2;i<MAX;i++){
    fact[i]=fact[i-1]*i%mod;
    invv[i]=mod-invv[mod%i]*(mod/i)%mod;
    finv[i]=finv[i-1]*invv[i]%mod;
  }
}
ll comb(ll n,ll k){
  if(n<k) return 0;
  if(n<0||k<0) return 0;
  return fact[n]*(finv[k]*finv[n-k]%mod)%mod;
}
struct Compress{
   vll a;
   int cnt;
   Compress() :cnt(0) {}
   void add(ll x){a.push_back(x);}
   void init(){
       sort(all(a));
       a.erase(unique(all(a)),a.end());
       cnt=a.size();
   }
   ll to(ll x){
       int index=lower_bound(all(a),x)-a.begin();
       return index;
   } //変換先
   ll from(ll x){return a[x];}//逆引き
   int size(){return cnt;}
};
struct UnionFind { 
    vector<int> par, siz; 
    UnionFind(int n) : par(n, -1) , siz(n, 1) { } 
    int root(int x) { 
        if (par[x] == -1) return x;
        else return par[x] = root(par[x]);
    }
    bool issame(int x, int y) {
        return root(x) == root(y);
    }
    bool unite(int x, int y) {
        x = root(x), y = root(y);
        if (x == y) return false; 
        if (siz[x] < siz[y]) swap(x, y);
        par[y] = x;
        siz[x] += siz[y];
        return true;
    }
    int size(int x) {
        return siz[root(x)];
    }
};

vll anss; 
void solve(int test){
    int n; cin >> n;
    vve g(n);
    rep(i,n-1){
        int a,b; cin >> a >> b;
        a--;b--;
        g[a].push_back(edge(b,1,i));
        g[b].push_back(edge(a,1,i));
    }
    vll dp(n,-inf);
    {
        auto dfs=[&](auto dfs,int v,int p=-1)->void {
            chmax(dp[v],0ll);
            for(auto u:g[v]){
                if(u.to==p)continue;
                dfs(dfs,u.to,v);
                chmax(dp[v],dp[u.to]+1);
            }
        };
        dfs(dfs,0,-1);
    }
    vll dp2(n,-inf);
    {
        auto dfs=[&](auto dfs,int v,int p=-1)->void {
            set<P> st;
            for(auto u:g[v]){
                if(u.to==p)continue;
                chmax(dp2[u.to],dp2[v]+1);
                st.insert(P(dp[u.to],u.to));
            }
            if(st.size()>=2){
                /*
                if(v==0){
                    cout << "test" << endl;
                    auto it=st.begin();
                    while(it!=st.end()){
                        cout << it->first  << " " << it->second << endl;
                        it++;
                    }
                }
                */
                for(auto u:g[v]){
                    if(u.to==p)continue;
                    auto it=st.lower_bound(P(dp[u.to],u.to));
                    st.erase(*it);
                    auto itb=st.rbegin();
                    chmax(dp2[u.to],itb->first+2);
                    /*
                    if(v==0){
                        cout <<"te "<< u.to+1 << " " << (itb->first+2) << endl;
                    }
                    */
                    st.insert(P(dp[u.to],u.to));
                }
            }
            for(auto u:g[v]){
                if(u.to==p)continue;
                dfs(dfs,u.to,v);
            }
        };
        dp2[0]=0;
        dfs(dfs,0,-1);
    }
    /*
    rep(v,n){
        cout << dp[v] << " " << dp2[v] << endl;
    }
    */
    vll ansv={-1,-1,-1};
    {
        vll dam={-1,-1,-1};
        vll maxv={-1,-1,-1};
        auto dfs=[&](auto dfs,int v,int p=-1)->void {
            vll vs;
            for(auto u:g[v]){
                if(u.to==p)continue;
                dfs(dfs,u.to,v);
                vs.push_back(dp[u.to]+1);
            }
            vs.push_back(dp2[v]);
            while(vs.size()<3)vs.push_back(0);
            sort(arr(vs));
            rep(i,3)dam[i]=vs[i];
            reverse(all(dam));
            vll damdam={dam[0]+dam[1],dam[1]+dam[2],dam[2]+dam[0]};
            sort(all(damdam));
            if(chmax(maxv,damdam)){
                ansv=dam;
            }
            /*
            if(chmax(ansv,dam)){
                cout << v+1 << endl;
                rep(i,3)cout << dam[i] << " ";
                cout << endl;
            }
            cout << v+1 << endl;
            for(auto val:vs)cout << val << " ";
            cout << endl;
            rep(i,3)cout << dam[i] << " ";
            cout << endl;
            */
        };
        dfs(dfs,0,-1);
    }
   // rep(v,n)cout << v+1 << " " << dp[v] << " " << dp2[v] << endl;
    mint ans=0;
    {
        int da=ansv[0];
        int db=ansv[1];
        int dc=ansv[2];
        ans+=mint(2).pow(da+1);
        ans+=mint(2).pow(db+1);
        ans+=mint(2).pow(dc+1);
        ans-=3;
        ans*=mint(2).pow(n-da-db-dc);
        ans=mint(2).pow(n+2)-ans;
        //cout <<da << " " <<db << " " <<dc << endl;
    }
    cout << ans.val() << endl;




}
//cat cf.cpp | pbcopy
//g++ cf.cpp -std=c++17 -I .  
int main(){cin.tie(0);ios::sync_with_stdio(false);
    //initcomb();
    int t=1;//cin >>t;
    rep(test,t)solve(test);
    for(auto ans:anss){
        cout<< ans << endl;
    }
}