UOJ67 新年的毒瘤 tarjan

题目传送门

题意：给出一个$N$个点、$M$条边的无向图，找出其中的点，满足去掉该点与和它相连的边之后，这个图会变成一棵树。$N , M \leq 10^5$

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说是毒瘤，真的不毒瘤

思考一下，我们需要找的就是度为$M - (N - 1 - 1)$且不是割点的点，直接tarjan即可

想起来在某luogu题解里把tarjan写成targan

 #include<bits/stdc++.h>
 #define MAXN 100001
 using namespace std;

 inline int read(){
     ;
     char c = getchar();
     while(!isdigit(c))
         c = getchar();
     while(isdigit(c)){
         a = (a << ) + (a << ) + (c ^ ');
         c = getchar();
     }
     return a;
 }

 struct Edge{
     int end , upEd;
 }Ed[MAXN << ];

 int head[MAXN] , dfn[MAXN] , low[MAXN] , in[MAXN] , ts , cntEd , N , M;
 bool vis[MAXN];

 inline void addEd(int a , int b){
     Ed[++cntEd].end = b;
     Ed[cntEd].upEd = head[a];
     head[a] = cntEd;
     in[a]++;
 }

 void tarjan(int a , int fa){
     dfn[a] = low[a] = ++ts;
     ;
     for(int i = head[a] ; i ; i = Ed[i].upEd)
         if(Ed[i].end != fa)
             if(!dfn[Ed[i].end]){
                 tarjan(Ed[i].end , a);
                 low[a] = min(low[Ed[i].end] , low[a]);
                 ch++;
                 )
                     vis[a] = ;
             }
             else
                 low[a] = min(low[a] , dfn[Ed[i].end]);
      && ch >= )
         vis[a] = ;
 }

 int main(){
     N = read();
     M = read();
      ; i <= M ; i++){
         int a = read() , b = read();
         addEd(a , b);
         addEd(b , a);
     }
     tarjan( , );
     ;
      ; i <= N ; i++)
          && !vis[i])
             ans++;
     cout << ans << endl;
      ; i <= N ; i++)
          && !vis[i])
             cout << i << ' ';
     ;
 }