| 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;
}