直接看代码
std::vector<int> d;
inline bool cmp(int a,int b){
return dfn[a]<dfn[b];
}
inline void build(){
std::sort(d.begin(),d.end(),cmp);
for(int i=d.size()-2;~i;i--)
d.push_back(LCA(d[i],d[i+1]));
std::sort(d.begin(),d.end(),cmp);
d.erase(std::unique(d.begin(),d.end()),d.end());
top=0;
for(int i=0;i<(int)d.size();i++){
int u=d[i];
while(top&&low[sta[top]]<dfn[u])top--;
if(top)fa[u]=sta[top];
sta[++top]=u;
}
}