結果
問題 | No.1333 Squared Sum |
ユーザー |
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提出日時 | 2021-09-23 15:50:48 |
言語 | C++14 (gcc 13.3.0 + boost 1.87.0) |
結果 |
AC
|
実行時間 | 187 ms / 2,000 ms |
コード長 | 2,576 bytes |
コンパイル時間 | 3,853 ms |
コンパイル使用メモリ | 233,724 KB |
実行使用メモリ | 40,704 KB |
最終ジャッジ日時 | 2024-07-05 09:27:50 |
合計ジャッジ時間 | 11,098 ms |
ジャッジサーバーID (参考情報) |
judge4 / judge5 |
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ファイルパターン | 結果 |
---|---|
other | AC * 44 |
ソースコード
#include <bits/stdc++.h>#include <atcoder/all>using namespace std;using namespace atcoder;using mint = modint1000000007;const int mod = 1000000007;//using mint = modint998244353;//const int mod = 998244353;//const int INF = 1e9;//const long long LINF = 1e18;//const bool debug = false;#define rep(i, n) for (int i = 0; i < (n); ++i)#define rep2(i,l,r)for(int i=(l);i<(r);++i)#define rrep(i, n) for (int i = (n-1); i >= 0; --i)#define rrep2(i,l,r)for(int i=(r-1);i>=(l);--i)#define all(x) (x).begin(),(x).end()#define allR(x) (x).rbegin(),(x).rend()#define endl "\n"#define P pair<long long,long long>template<typename A, typename B> inline bool chmax(A & a, const B & b) { if (a < b) { a = b; return true; } return false; }template<typename A, typename B> inline bool chmin(A & a, const B & b) { if (a > b) { a = b; return true; } return false; }struct Edge {int to;mint cost;Edge(int _to, mint _cost) :to(_to), cost(_cost) {}};struct Data {mint sump;mint sum;mint count;Data() :sump(0), sum(0), count(0) {}Data(mint _sump, mint _sum, mint _count) :sump(_sump), sum(_sum), count(_count) {}};vector<Edge>g[200005];vector<Data>dp(200005);vector<Data>dpR(200005);void dfs(int v, int p = -1) {Data val = { 0,0,0 };for (auto e : g[v]) {if (p == e.to)continue;dfs(e.to, v);val.sump += dp[e.to].sump + dp[e.to].sum * e.cost * 2 + e.cost * e.cost * (dp[e.to].count + 1);val.sum += dp[e.to].sum + e.cost * (dp[e.to].count + 1);val.count += dp[e.to].count + 1;}dp[v] = val;}void dfsR(int v, int p = -1, mint cost = 0) {dpR[v] = dp[v];if (-1 != p) {Data sub = dpR[p];sub.sump -= dp[v].sump + dp[v].sum * cost * 2 + cost * cost * (dp[v].count + 1);sub.sum -= dp[v].sum + cost * (dp[v].count + 1);sub.count -= dp[v].count + 1;dpR[v].sump += sub.sump + sub.sum * cost * 2 + cost * cost * (sub.count + 1);dpR[v].sum += sub.sum + cost * (sub.count + 1);dpR[v].count += sub.count + 1;}for (auto e : g[v]) {if (p == e.to)continue;dfsR(e.to, v, e.cost);}}int main() {ios::sync_with_stdio(false);cin.tie(nullptr);int n; cin >> n;rep(i, n - 1) {int a, b, c; cin >> a >> b >> c; a--; b--;g[a].push_back({ b,c });g[b].push_back({ a,c });}dfs(0);//rep(i, n)cout << dp[i].sump.val() << " " << dp[i].sum.val() << " " << dp[i].count.val() << endl;dfsR(0);//rep(i, n)cout << dpR[i].sump.val() << " " << dpR[i].sum.val() << " " << dpR[i].count.val() << endl;mint ans = 0;rep(i, n)ans += dpR[i].sump;ans *= inv_mod(2, mod);cout << ans.val() << endl;return 0;}