tarjan割点和割边[模板]

割点

int low[maxn],dfn[maxn],stac[maxn],vis[maxn],sd[maxn];
int cut[maxn],bridge[maxn],id,top;
void tarjan(int u,int fa)
{
  low[u]=dfn[u]=++id;
  int child=0;
  for(int i=head[u];i;i=d[i].nxt )
  {
    int v=d[i].to;
    if( !dfn[v] )
    {
      tarjan(v,fa),low[u]=min( low[u],low[v] );
      if( low[v]>=dfn[u]&&u!=fa ) cut[u]=1;//u是割点
      if( u==fa ) child++; 
    }
    low[u]=min( low[u],dfn[v] );
  }
  if( child>=2&&u==fa ) cut[u]=1;
}

割边

int low[maxn],dfn[maxn],stac[maxn],vis[maxn],sd[maxn];
int cut[maxn],bridge[maxn],id,top;
void tarjan(int u,int fa)
{
  low[u]=dfn[u]=++id;
  for(int i=head[u];i;i=d[i].nxt )
  {
    int v=d[i].to;
    if( !dfn[v] )
    {
      tarjan(v,u),low[u]=min( low[u],low[v] );
      if( low[v]>dfn[u])  bridge[i]=1;
    }
    else if( v!=fa )
      low[u]=min( low[u],dfn[v] );
  }
}