比赛 2025.10.24 评测结果 WWWWWWWWWW
题目名称 编辑题目 最终得分 0
用户昵称 梦那边的美好TE 运行时间 3.843 s
代码语言 C++ 内存使用 76.20 MiB
提交时间 2025-10-24 11:46:46
显示代码纯文本
#include <bits/stdc++.h>
using namespace std;
const int mod=998244353;
const int N=1e6+10,M=2e6+10;
int n,m,ver[N],to[M],nxt[M],val[M],idx=1,mk[M],w[N];
int dfn[N],low[N],tot,dcc,id[M],from[N],ID,dn[N];
int vis[N],cnt,siz[N],fath[N];
map<int,int>H;
vector<int>G[N],Edge[N];
long long ksm(long long a,long long b){
	long long ans=1;
	while(b){
		if(b&1)ans=ans*a%mod;
		a=a*a%mod;
		b>>=1;
	}
	return ans;
}
void add(int x,int y,int z){
	to[++idx]=y,nxt[idx]=ver[x],ver[x]=idx,val[idx]=z;
}
void tarjan(int u,int edge){
	dfn[u]=low[u]=++tot;
	for(int i=ver[u];i;i=nxt[i]){
		int v=to[u];
		if(!dfn[v]){
			tarjan(v,i);
			low[u]=min(low[u],low[v]);
			if(low[v]>dfn[u])mk[i]=mk[i^1]=1;
		}else if((i^1)!=edge){
			low[u]=min(low[u],dfn[v]);
		}
	}
	return;
}
void dfs(int x){
	from[x]=dcc,w[dcc]++,vis[x]=1;
	for(int i=ver[x];i;i=nxt[i]){
		if(mk[i])continue;
		id[i]=id[i^1]=dcc;
		int y=to[i];
		if(!vis[y])dfs(y);
	}
	return;
}
void Add(int x,int y){
	G[x].push_back(y);
}
void DFS(int x,int fa){
	dn[x]=++cnt,siz[x]=1;
	fath[x]=fa;
	for(auto y:G[x]){
		if(y==fa)continue;
		DFS(y,x);
		siz[x]+=siz[y];
	}
	return;
}
int c[N];
int askv(int u){
	return w[dn[u]+siz[u]-1]-w[dn[u]-1];
}
void add(int x,int y){
	for(;x<=dcc;x+=(x&-x))c[x]+=y;
	return;
}
int ask(int x){
	int cnt=0;
	for(;x>0;x-=(x&-x))cnt+=c[x];
	return cnt;
}
int main(){
	freopen("edit.in","r",stdin);
	freopen("edit.out","w",stdout); 
	scanf("%d %d",&n,&m);
	for(int i=1,u,v,val;i<=m;i++){
		scanf("%d %d %d",&u,&v,&val);
		if(!H.count(val))H[val]=++ID;
		val=H[val],add(u,v,val),add(v,u,val);
		Edge[val].push_back(idx);
	}
	for(int i=1;i<=n;i++)if(!dfn[i])tarjan(1,0);
	for(int i=1;i<=n;i++){
		if(!vis[i]){
			dcc++;
			dfs(i);
		}
	}
	for(int i=1;i<=n;i++){
		for(int j=ver[i];j;j=nxt[j]){
			if(from[i]!=from[to[j]]){
				Add(from[i],from[to[j]]);
			}
		}
	}
	long long ans=n*m;
	DFS(1,0);
	for(int i=1;i<=cnt;i++)w[i]+=w[i-1];
	for(int i=1;i<=ID;i++){
		if(Edge[i].size()==1){
			ans-=n;
		}else{
			int u,v;
			for(auto pat:Edge[i]){
				u=to[pat],v=to[pat^1];
				if(!mk[pat])add(id[pat],1);
				else{
					u=from[u],v=from[v];
					if(u==fath[v])swap(u,v);
					add(u,1);
				}
			}
			for(auto pat:Edge[i]){
				if(mk[pat]){
					u=from[u],v=from[v];
					if(u==fath[v])swap(u,v);
					if(!ask(u))ans-=askv(u);
					if(ask(u)==Edge[i].size())ans-=n-askv(u);
				}
			}
			for(auto pat:Edge[i]){
				u=to[pat],v=to[pat^1];
				if(!mk[pat])add(id[pat],-1);
				else{
					u=from[u],v=from[v];
					if(u==fath[v])swap(u,v);
					add(u,-1);
				}
			}
		}
	}
	ans%=mod;
	ans=ans*ksm(1ll*n*m%mod,mod-2)%mod;
	//printf("%lld\n",ans);
	return 0;
}