結果

問題 No.1333 Squared Sum
コンテスト
ユーザー 沙耶花
提出日時 2021-03-04 21:18:13
言語 C++17
(gcc 13.3.0 + boost 1.87.0)
結果
AC  
実行時間 1,231 ms / 2,000 ms
コード長 4,790 bytes
コンパイル時間 3,491 ms
コンパイル使用メモリ 230,236 KB
最終ジャッジ日時 2025-01-19 10:06:42
ジャッジサーバーID
（参考情報） 		judge5 / judge3
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ファイルパターン 結果
other AC * 44
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コンパイルメッセージ
main.cpp: In function ‘int main()’:
main.cpp:208:22: warning: ignoring return value of ‘int scanf(const char*, ...)’ declared with attribute ‘warn_unused_result’ [-Wunused-result]
  208 |                 scanf("%d %d %d",&u,&v,&w);
      |                 ~~~~~^~~~~~~~~~~~~~~~~~~~~

ソースコード

diff # 

#include <stdio.h>
#include <bits/stdc++.h>
#include <atcoder/modint>
using namespace atcoder;
using mint = modint1000000007;
using namespace std;
#define rep(i,n) for (int i = 0; i < (n); ++i)
#define Inf 1000000000000000000

struct centroid_tree{
	
	vector<vector<int>> E;
	vector<int> cnt;
	int r;
	
	vector<int> depth;
	vector<vector<int>> pos;
	vector<vector<int>> bind;
	vector<vector<int>> childs;
	
	centroid_tree(vector<vector<int>> argE){
		int n = argE.size();
		E.resize(n,vector<int>());

		cnt.resize(n);
		r = go(0,argE);
		
		depth.resize(n);
		pos.resize(n);
		bind.resize(n);
		childs.resize(n);
		dfs(r,-1,E);
		build(r,0);
		
	}
	
	int go(int a,vector<vector<int>> &argE){
		
		dfs(a,-1,argE);
		
		int sz = cnt[a];
		
		int ret = dfs2(a,-1,argE,sz);

		rep(i,argE[ret].size()){
			int to = argE[ret][i];
			argE[to].erase(find(argE[to].begin(),argE[to].end(),ret));
			
			int g = go(to,argE);
			E[ret].push_back(g);
		}
		argE[ret].clear();

		return ret;
		
	}
	
	void dfs(int cur,int p,vector<vector<int>> &argE){
		cnt[cur] = 1;
		rep(i,argE[cur].size()){
			int to = argE[cur][i];
			if(to==p)continue;
			dfs(to,cur,argE);
			cnt[cur] += cnt[to];
		}
	}
	
	int dfs2(int cur,int p,vector<vector<int>> &argE,int sz){
		int ret = -1;
		int m = 0;
		rep(i,argE[cur].size()){
			int to = argE[cur][i];
			if(to==p)continue;
			ret = dfs2(to,cur,argE,sz);
			if(ret!=-1)return ret;
			m = max(m,cnt[to]);
		}
		
		if(sz-cnt[cur]<=sz/2 && m<=sz/2){
			ret = cur;
		}
		return ret;
		
	}
	
	void build(int cur,int d){
		depth[cur] = d;
		bind[cur].push_back(0);
		rep(i,E[cur].size()){
			int to = E[cur][i];
			build(to,d+1);
			rep(j,childs[to].size()){
				int x = childs[to][j];
				childs[cur].push_back(x);
				if(pos[x].size()<=d)pos[x].resize(d+1,-1);
				pos[x][d] = i;
			}
			bind[cur].push_back(childs[cur].size());
		}
		int x = cur;
		childs[cur].push_back(x);
		if(pos[x].size()<=d)pos[x].resize(d+1,-1);
		pos[x][d] = E[cur].size();
		bind[cur].push_back(childs[cur].size());
	}
	
};

struct HLD{
	vector<int> sz,parent,depth,root,pos;
	vector<int> arr;
	HLD(vector<vector<int>> &E){
		sz.resize(E.size(),1);
		parent.resize(E.size(),0);
		depth.resize(E.size(),0);
		root.resize(E.size(),0);
		pos.resize(E.size(),0);
		
		dfs(0,-1,E);
		dfs2(0,-1,E,0);
	}
	
	void dfs(int now,int p,vector<vector<int>> &E){
		parent[now] = p;
		if(p==-1){
			depth[now] = 0;
		}
		else{
			depth[now] = depth[p]+1;
		}
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p)continue;
			dfs(to,now,E);
			sz[now] += sz[to];
		}
	}
	
	void dfs2(int now,int p,vector<vector<int>> &E,int r){
		pos[now] = arr.size();
		arr.push_back(now);
		root[now] = r;
		int maxi = 0;
		int ind = -1;
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p)continue;
			if(maxi<sz[to]){
				maxi = sz[to];
				ind = to;
			}
		}
		if(ind==-1)return;
		dfs2(ind,now,E,r);
		for(int i=0;i<E[now].size();i++){
			int to = E[now][i];
			if(to==p||to==ind)continue;
			dfs2(to,now,E,to);
		}
	}
	
	vector<pair<int,int>> query(int u,int v){
		vector<pair<int,int>> ret;
		int t = 0;
		while(root[u]!=root[v]){
			if(depth[root[u]] <= depth[root[v]]){
				ret.insert(ret.begin()+t,{pos[root[v]], pos[v]});
				v = parent[root[v]];
			}
			else{
				ret.insert(ret.begin()+t,{pos[u],pos[root[u]]});
				u = parent[root[u]];
				t++;
			}
		}
		ret.insert(ret.begin()+t,{pos[u],pos[v]});
		return ret;
	}
	
	int lca(int u,int v){
		for(;;v=parent[root[v]]){
			if(pos[u]>pos[v])swap(u,v);
			if(root[u]==root[v])return u;
		}
	}
	
	int get_distance(int u,int v){
		return depth[u] + depth[v] - 2 * depth[lca(u,v)];
	}
	
};

mint get_dis(HLD &H,vector<mint> &S,int u,int v){
	int l = H.lca(u,v);
	mint ret = S[u] + S[v] - S[l]*2;
	return ret;
}

int main(){
	
	int n;
	cin>>n;
	
	vector<vector<int>> E(n);
	vector<vector<pair<int,mint>>> E2(n);
	rep(i,n-1){
		int u,v,w;
		scanf("%d %d %d",&u,&v,&w);
		u--;v--;
		E[u].push_back(v);
		E[v].push_back(u);
		E2[u].emplace_back(v,w);
		E2[v].emplace_back(u,w);
	}
	
	centroid_tree C(E);

	HLD H(E);

	vector<mint> dis(n,0);
	vector<bool> visited(n,false);
	queue<int> Q;
	Q.push(0);
	visited[0] = true;
	while(Q.size()>0){
		int u = Q.front();
		Q.pop();
		rep(i,E2[u].size()){
			int v = E2[u][i].first;
			mint w = E2[u][i].second;
			if(visited[v])continue;
			visited[v] = true;
			dis[v] = dis[u] + w;
			Q.push(v);
		}
	}
	
	mint ans = 0;
	
	rep(i,n){
		mint sum = 0;
		mint temp = 0;
		int cur = 0;
		rep(j,C.childs[i].size()){
			mint d = get_dis(H,dis,i,C.childs[i][j]);
			ans += d*d * (C.bind[i].back() - (C.bind[i][cur+1] - C.bind[i][cur]));
			ans += d*2*sum;
			temp += d;
			if(j+1 == C.bind[i][cur+1]){
				cur++;
				sum += temp;
				temp = 0;
			}
		}
	}
	
	cout<<ans.val()<<endl;
	
    return 0;
}
0