UOJ#67. 新年的毒瘤

传送门

练习一下Tarjan的模板。

求一下割点，然后加个约束条件判一下特殊点，剩下的就是所求点。

//UOJ 67
//by Cydiater
//2016.10.27
#include <iostream>
#include <iomanip>
#include <cmath>
#include <ctime>
#include <cstring>
#include <string>
#include <algorithm>
#include <queue>
#include <map>
#include <cstdio>
#include <bitset>
#include <cstdlib>
using namespace std;
#define ll long long
#define up(i,j,n)		for(int i=j;i<=n;i++)
#define down(i,j,n)		for(int i=j;i>=n;i--)
#define cmin(a,b) a=min(a,b)
#define cmax(a,b) a=max(a,b)
const int MAXN=2e5+5;
const int oo=0x3f3f3f3f;
inline int read(){
	char ch=getchar();int x=0,f=1;
	while(ch>'9'||ch<'0'){if(ch=='-')f=-1;ch=getchar();}
	while(ch>='0'&&ch<='9'){x=x*10+ch-'0';ch=getchar();}
	return x*f;
}
int N,M,LINK[MAXN],len=0,dfn[MAXN],low[MAXN],dfs_clock=0,siz[MAXN],ans=0,outdu[MAXN];
bool vis[MAXN],OK[MAXN];
struct edge{
	int y,next;
}e[MAXN];
namespace solution{
	inline void insert(int x,int y){e[++len].next=LINK[x];LINK[x]=len;e[len].y=y;}
	void init(){
		N=read();M=read();
		up(i,1,M){
			int x=read(),y=read();
			insert(x,y);
			insert(y,x);
			siz[x]++;siz[y]++;
		}
	}
	void tarjan(int node,int father){
		vis[node]=1;dfn[node]=low[node]=++dfs_clock;
		for(int i=LINK[node];i;i=e[i].next)if(e[i].y!=father){
			if(!dfn[e[i].y]){
				outdu[node]++;
				tarjan(e[i].y,node);
				cmin(low[node],low[e[i].y]);
				if(low[e[i].y]>=dfn[node])OK[node]=1;
			}else if(vis[e[i].y]) cmin(low[node],dfn[e[i].y]);
		}
		if(M-siz[node]!=N-2)OK[node]=1;
		if(outdu[node]==1&&node==1&&M-siz[node]==N-2)OK[node]=0;
		if(OK[node])ans++;
	}
	void slove(){
		up(i,1,N)if(!dfn[i])tarjan(i,0);
	}
	void output(){
		cout<<N-ans<<endl;
		up(i,1,N)if(!OK[i])printf("%d ",i);
	}
}
int main(){
	//freopen("input.in","r",stdin);
	using namespace solution;
	init();
	slove();
	output();
	return 0;
}