結果

問題 No.1333 Squared Sum
ユーザー Chanyuh
提出日時 2021-01-08 23:59:44
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 250 ms / 2,000 ms
コード長 4,514 bytes
コンパイル時間 1,174 ms
コンパイル使用メモリ 125,888 KB
最終ジャッジ日時 2025-01-17 14:46:24
ジャッジサーバーID
（参考情報） 		judge3 / judge5
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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

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プレゼンテーションモードにする

#include<iostream>
#include<array>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<complex>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<utility>
#include<tuple>
#include<cassert>
using namespace std;
typedef long long ll;
typedef unsigned int ui;
const ll mod = 1000000007;
const ll INF = (ll)1000000007 * 1000000007;
typedef pair<int, int> P;
#define stop char nyaa;cin>>nyaa;
#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define Per(i,sta,n) for(int i=n-1;i>=sta;i--)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
typedef long double ld;
const ld eps = 1e-8;
const ld pi = acos(-1.0);
typedef pair<ll, ll> LP;
int dx[4]={1,-1,0,0};
int dy[4]={0,0,1,-1};
template<class T>bool chmax(T &a, const T &b) {if(a<b){a=b;return 1;}return 0;}
template<class T>bool chmin(T &a, const T &b) {if(b<a){a=b;return 1;}return 0;}
template<int mod>
struct ModInt {
    long long x;
    static constexpr int MOD = mod;
 
    ModInt() : x(0) {}
    ModInt(long long y) : x(y >= 0 ? y % mod : (mod - (-y) % mod) % mod) {}
    explicit operator int() const {return x;}
 
    ModInt &operator+=(const ModInt &p) {
        if((x += p.x) >= mod) x -= mod;
        return *this;
    }
    ModInt &operator-=(const ModInt &p) {
        if((x += mod - p.x) >= mod) x -= mod;
        return *this;
    }
    ModInt &operator*=(const ModInt &p) {
        x = (int)(1LL * x * p.x % mod);
        return *this;
    }
    ModInt &operator/=(const ModInt &p) {
        *this *= p.inverse();
        return *this;
    }
 
    ModInt operator-() const { return ModInt(-x); }
    ModInt operator+(const ModInt &p) const { return ModInt(*this) += p; }
    ModInt operator-(const ModInt &p) const { return ModInt(*this) -= p; }
    ModInt operator*(const ModInt &p) const { return ModInt(*this) *= p; }
    ModInt operator/(const ModInt &p) const { return ModInt(*this) /= p; }
    ModInt operator%(const ModInt &p) const { return ModInt(0); }         
 
    bool operator==(const ModInt &p) const { return x == p.x; }
    bool operator!=(const ModInt &p) const { return x != p.x; }
 
    ModInt inverse() const{
        int a = x, b = mod, u = 1, v = 0, t;
        while(b > 0) {
            t = a / b;
            a -= t * b;
            swap(a, b);
            u -= t * v;
            swap(u, v);
        }
        return ModInt(u);
    }
    ModInt power(long long n) const {
        ModInt ret(1), mul(x);
        while(n > 0) {
            if(n & 1)
            ret *= mul;
            mul *= mul;
            n >>= 1;
        }
        return ret;
    }
    ModInt power(const ModInt p) const{
        return ((ModInt)x).power(p.x);
    }
    friend ostream &operator<<(ostream &os, const ModInt<mod> &p) {
        return os << p.x;
    }
    friend istream &operator>>(istream &is, ModInt<mod> &a) {
        long long x;
        is >> x;
        a = ModInt<mod>(x);
        return (is);
    }
};
using modint = ModInt<mod>;
struct edge{
    int to;modint l;
    edge(){}
    edge(int to,modint l):to(to),l(l){}
};
int n;
vector<edge> G[200010];
modint Z[200010],Z_sum[200010],Z_all=0;int sub[200010];
modint ans=0;
void dfs1(int s,int par,modint l){
    sub[s]=1;
    for(edge e:G[s]){
        if(e.to==par) continue;
        dfs1(e.to,s,e.l);
        sub[s]+=sub[e.to];
        Z_sum[s]+=Z_sum[e.to]+Z[e.to];
    }
    Z[s]=l*sub[s];
}
void dfs2(int s,int par,modint l,modint Z_par){
    for(edge e:G[s]){
        if(e.to==par) continue;
        dfs2(e.to,s,e.l,Z_par+l*(n-sub[s])+Z_sum[s]-Z_sum[e.to]-Z[e.to]);
    }
    if(par!=-1){
        ans+=l*l*sub[s]*(n-sub[s]);
        ans+=l*Z_sum[s]*(n-sub[s]);
        ans+=l*Z_par*sub[s];
    }
    //cout << s << " " << l << " " << Z_par << " " << Z_sum[s] << " " << ans << endl;
}
void solve(){
    cin >> n;
    rep(i,n-1){
        int a,b;modint l;cin >> a >> b >> l;a--;b--;
        G[a].push_back({b,l});
        G[b].push_back({a,l});
    }
    dfs1(0,-1,0);
    // rep(i,n){
    //     cout << i << " " << sub[i] << " " << Z[i] << " " << Z_sum[i] << endl;
    // }
    dfs2(0,-1,0,0);
    cout << ans << endl;
}
int main(){
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(50);
    solve();
}
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