AW363 B城

题目地址

---

简述：

• 割点+方案统计（乘法原理）

易错点：

• 必须开long long.
• 边要开到2e6.
• 初始化dfn[x]时候需要一块初始化low[x].
• 输出时需要使用"%lld ".

---

#include<cstdio>
#include<iostream>
#define ll long long
using namespace std;
const int MAXN=2e5,MAXM=2e6;
struct Edge{
	int from,to,w,nxt;
}e[MAXM];
int head[MAXN],edgeCnt=1;
void addEdge(int u,int v,int w){
	e[++edgeCnt].from=u;
	e[edgeCnt].to=v;
	e[edgeCnt].w=w;
	e[edgeCnt].nxt=head[u];
	head[u]=edgeCnt;
}
int dfn[MAXN],dfnCnt=0,low[MAXN],siz[MAXN];
bool cut[MAXN];
int s,n;
ll ans[MAXN];
void tarjan(int x){
	dfn[x]=low[x]=++dfnCnt;
	siz[x]=1;
	int cutNum=0,sonSum=0;
	for(int i=head[x];i;i=e[i].nxt){
		int nowV=e[i].to;
		if(!dfn[nowV]){
			tarjan(nowV);
			siz[x]+=siz[nowV];
			low[x]=min(low[x],low[nowV]);
			if(low[nowV]>=dfn[x]){
				cutNum++;
				if(x!=s||cutNum>1)cut[x]=1;
				sonSum+=siz[nowV];
				ans[x]+=(ll)siz[nowV]*(n-siz[nowV]);//son to others
			}
		}else low[x]=min(low[x],dfn[nowV]);
	}
	if(cut[x])ans[x]+=(ll)(n-(sonSum+1))*(sonSum+1)+(n-1);//others to us+me to others
	else ans[x]=2*(n-1);//x to others
}
int main(){
	int m;
	scanf("%d%d",&n,&m);
	for(int i=1;i<=m;i++){
		int u,v;
		scanf("%d%d",&u,&v);
		addEdge(u,v,1);
		addEdge(v,u,1);
	}
	s=1;
	tarjan(s);
	for(int i=1;i<=n;i++)
		printf("%lld
",ans[i]);
	return 0;
}