Tarjan 割点割边模板

Posted 2020-09-19

 1 #include <algorithm>
 2 #include <cstring>
 3 #include <cstdio>
 4 
 5 using namespace std;
 6 
 7 const int N(100000+15);
 8 int n,m,u,v;
 9 int head[N],sumedge;
10 struct Edge
11 {
12     int to,next;
13     Edge(int to=0,int next=0) :
14         to(to),next(next){}
15 }edge[N<<1];
16 
17 void ins(int from,int to)
18 {
19     edge[++sumedge]=Edge(to,head[from]);
20     head[from]=sumedge;
21 }
22 
23 int dfn[N],low[N],tim;
24 int cutpoint[N],cutedge[N],sum;
25 
26 void DFS(int now,int pre)
27 {
28     low[now]=dfn[now]=++tim;
29     int sumtredge=0,if_cutpoint=0;
30     for(int i=head[now];i!=-1;i=edge[i].next)
31         if((i^1)!=pre)
32         {
33             int go=edge[i].to;
34             if(!dfn[go])
35             {
36                 sumtredge++;
37                 DFS(go,i);
38                 if(low[go]>=dfn[now]) if_cutpoint=1;
39                 if(low[go]>dfn[now]) cutedge[i>>1]=true;
40                 low[now]=min(low[now],low[go]);
41             }
42             else low[now]=min(low[now],dfn[go]);
43           }
44     if(pre==-1)
45     {
46         if(sumtredge>1)  cutpoint[now]=true;
47     }
48     else if(if_cutpoint) cutpoint[now]=true;
49 }
50 
51 int main()
52 {
53     /*freopen("made.txt","r",stdin);
54     freopen("myout.txt","w",stdout);*/
55     
56     scanf("%d%d",&n,&m);
57     sumedge=-1; //使边之间更有关系
58     memset(head,-1,sizeof(head));
59     for(int i=1;i<=m;i++)
60     {
61         scanf("%d%d",&u,&v);
62         ins(u,v);
63         ins(v,u);
64     }
65     for(int i=1;i<=n;i++) 
66         if(!dfn[i]) DFS(i,-1);
67     for(int i=1;i<=n;i++)
68         if(cutpoint[i]) printf("%d ",i);
69     printf("\n");
70     for(int i=0;i<sumedge;i++)
71         if(cutedge[i]) printf("%d ",i);
72     return 0;
73 }