結果

問題 No.1333 Squared Sum
ユーザー milanis48663220milanis48663220
提出日時 2021-01-08 23:19:06
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 237 ms / 2,000 ms
コード長 3,411 bytes
コンパイル時間 1,151 ms
コンパイル使用メモリ 94,836 KB
最終ジャッジ日時 2025-01-17 14:34:05
ジャッジサーバーID
(参考情報)
judge4 / 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 <iostream>
#include <algorithm>
#include <iomanip>
#include <vector>
#include <queue>
#include <set>
#include <map>
#include <cassert>
#define debug_value(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << #x << "=" << x << endl;
#define debug(x) cerr << "line" << __LINE__ << ":<" << __func__ << ">:" << x << endl;
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return 1; } return 0; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return 1; } return 0; }
using namespace std;
typedef long long ll;
const ll MOD = 1000000007;
class ModInt{
public:
ll v;
ModInt(ll _v = 0){
if(_v >= MOD) _v %= MOD;
v = _v;
}
ModInt operator+(ll n){
return ModInt((v+n)%MOD);
}
ModInt operator-(ll n){
return ModInt((v-n+MOD)%MOD);
}
ModInt operator*(ll n){
if(n >= MOD) n %= MOD;
return ModInt((v*n)%MOD);
}
ModInt operator/(ll n){
return ModInt((ModInt(n).inv()*v).v%MOD);
}
void operator+=(ll n){
v = (v+n)%MOD;
}
void operator-=(ll n){
v = (v-n+MOD)%MOD;
}
void operator*=(ll n){
v = (v*n)%MOD;
}
ModInt operator+(ModInt n){
return ModInt((v+n.v)%MOD);
}
ModInt operator-(ModInt n){
return ModInt((v-n.v+MOD)%MOD);
}
ModInt operator*(ModInt n){
return ModInt((v*n.v)%MOD);
}
ModInt operator/(ModInt n){
return ModInt((n.inv()*v).v%MOD);
}
void operator+=(ModInt n){
v = (v+n.v)%MOD;
}
void operator-=(ModInt n){
v = (v-n.v+MOD)%MOD;
}
void operator*=(ModInt n){
v = (v*n.v)%MOD;
}
void operator=(ModInt n){
v = n.v;
}
void operator=(ll n){
v = n;
}
ModInt inv(){
if(v == 1) return ModInt(1);
else return ModInt(MOD-ModInt(MOD%v).inv().v*(MOD/v)%MOD);
}
};
ostream& operator<<(ostream& os, const ModInt& m){
os << m.v;
return os;
}
istream & operator >> (istream &in, ModInt &m){
in >> m.v;
return in;
}
ModInt dp_sum[200000];
ModInt dp_square[200000];
ModInt cnt_ch[200000];
struct edge{
int to;
ModInt cost;
};
int n;
vector<edge> G[200000];
ModInt ans;
bool used[200000];
void dfs(int v){
used[v] = true;
vector<edge> visited;
for(auto e : G[v]){
if(!used[e.to]){
visited.push_back(e);
dfs(e.to);
cnt_ch[v] += cnt_ch[e.to];
dp_square[v] += dp_square[e.to]+dp_sum[e.to]*e.cost*2+e.cost*e.cost*cnt_ch[e.to];
dp_sum[v] += dp_sum[e.to]+e.cost*cnt_ch[e.to];
}
}
for(edge e : visited){
ModInt x = dp_square[e.to]+dp_sum[e.to]*e.cost*2+e.cost*e.cost*cnt_ch[e.to];
ans += x*(cnt_ch[v]-cnt_ch[e.to]);
x = dp_sum[e.to]+e.cost*cnt_ch[e.to];
ans += x*(dp_sum[v]-x);
}
ans += dp_square[v];
cnt_ch[v]+=1;
// cout << v << ' ' << dp_sum[v] << ' ' << dp_square[v] << ' ' << ans << ' ' << cnt_ch[v] << endl;
}
int main(){
ios::sync_with_stdio(false);
cin.tie(0);
cout << setprecision(10) << fixed;
cin >> n;
for(int i = 0; i < n-1; i++){
int u, v;
ModInt w;
cin >> u >> v >> w;
u--; v--;
G[u].push_back((edge){v, w});
G[v].push_back((edge){u, w});
}
dfs(0);
cout << ans << endl;
}
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