結果

問題 No.1333 Squared Sum
ユーザー tokusakurai
提出日時 2021-01-08 23:01:10
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 298 ms / 2,000 ms
コード長 4,412 bytes
コンパイル時間 2,541 ms
コンパイル使用メモリ 203,532 KB
最終ジャッジ日時 2025-01-17 13:59:25
ジャッジサーバーID
（参考情報） 		judge1 / judge2
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ファイルパターン 結果
other AC * 44
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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(ll 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(ll k) const{
        Mod_Int now = *this, ret = 1;
        for(; k; 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){
        ll a;
        is >> a;
        p = Mod_Int<mod>(a);
        return is;
    }
};
using mint = Mod_Int<MOD>;
template<typename T>
struct Weighted_Graph{
    struct edge{
        int to; T cost;
        edge(int to, T cost) : to(to), cost(cost) {}
    };
    vector<vector<edge>> es;
    vector<T> si, s1, s2;
    T ans;
    const T INF_T;
    const int n;
    Weighted_Graph(int n) : INF_T(numeric_limits<T>::max()/2), n(n){
        es.resize(n);
        si.resize(n), s1.resize(n), s2.resize(n);
        ans = 0;
    }
    void add_edge(int from, int to, T cost, bool directed = false){
        es[from].eb(to, cost);
        if(!directed) es[to].eb(from, cost);
    }
    void dfs(int now, int pre){
        si[now] = 1, s1[now] = 0, s2[now] = 0;
        mint S = 0;
        vector<mint> a, b;
        
        each(e, es[now]){
            if(e.to == pre) continue;
            dfs(e.to, now);
            si[now] += si[e.to];
            mint x1 = s1[e.to]+si[e.to]*e.cost;
            mint x2 = s2[e.to]+s1[e.to]*2*e.cost+si[e.to]*e.cost*e.cost;
            s1[now] += x1, s2[now] += x2;
            ans += x2;
            S += x1*x1;
            a.eb(x2), b.eb(si[e.to]);
        }
        rep(i, sz(a)){
            ans += a[i]*(si[now]-1-b[i]);
        }
        ans += s1[now]*s1[now]-S;
    }
    void solve(){
        dfs(0, -1);
        cout << ans << '\n';
    }
};
int main(){
    int N;
    cin >> N;
    Weighted_Graph<mint> G(N);
    rep(i, N-1){
        int u, v; mint w;
        cin >> u >> v >> w; u--, v--;
        G.add_edge(u, v, w);
    }
    G.solve();
}
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