Home (tarjan V-DCC double point method for finding connected components and compression Determining the cut point) Template title

As a board question on the second question it is relaxed and less than an hour to beat even the complete code did not play.

About tarjan cut point of note:

1. In this board we seek is V-DCC, rather than shrink point, V-DCC least two dots, is shown in the block out any

And even edge that point, the same connectivity, but the way it is cut point mark on low [to]> = dfn [x] in later operations

The cut point is connected with the link block edges, so that in the worst case born point (i.e., picture of one strand) is 2 * n-2

If the number of edges is generally not explicitly given as 8 times points.

****** (This question 80 points, is to open a small array, not speed up the reading) *******

2. When we divided each block tarjan the Unicom, while (top! = To), since x may belong to a plurality of link blocks, we

You can not be popped, but it can be placed in block

3.else use in low dfn update, because otherwise we will update all nodes to 1, there is no need to determine whether or not to fa

2. Since the determination condition has> =;

4. The multi-emptied measurement! ! ! ! ! ! ! ! ! ! ! ! ! !

 

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<cstring>
  4 #include<string>
  5 #include<algorithm>
  6 #include<cmath>
  7 #include<stack>
  8 #include<map>
  9 #include<queue>
 10 #define ps push_back
 11 #define MAXN 405101
 12 #define ll long long
 13 using namespace std;
 14 int read()
 15 {
 16    char c=getchar();int x=0;
 17    while(c<'0'||c>'9')
 18    {
 19         c=getchar();
 20    }
 21    while(c>='0'&&c<='9')
 22    {
 23       x=(x<<1)+(x<<3)+(c^48);
 24       c=getchar();
 25    }
 26    return x;
 27 }
 28 int dfn[MAXN],low[MAXN],cut[MAXN],de;
 29 int vis[MAXN];
 30 int num_id,cnt;
 31 int belong[MAXN];
 32 vector<int>v[MAXN];
 33 stack<int>q;
 34 struct node{int to,n;}e1[MAXN*4],e2[MAXN*4];
 35 int head1[MAXN],head2[MAXN];int tot1,tot2;
 36 void add1(int u,int v)
 37 {
 38     e1[++tot1].to=v;e1[tot1].n=head1[u];head1[u]=tot1;
 39 }
 40 void add2(int u,int v)
 41 {
 42     e2[++tot2].to=v;e2[tot2].n=head2[u];head2[u]=tot2;
 43 }
 44 void tarjan(int x)
 45 {
 46    dfn[x]=low[x]=++de;vis[x]=1;q.push(x);
 47    int ss=0;
 48    for(int i=head1[x];i;i=e1[i].n)
 49    {
 50       int to=e1[i].to;
 51       if(dfn[to]==0)
 52       {         
 53           tarjan(to);
 54           low[x]=min(low[x],low[to]);
 55           if(low[to]>=dfn[x])
 56           {
 57               ss++;
 58               if(x!=1||ss>1)
 59               {
 60                   cut[x]=1;  
 61               }
 62               cnt++;
 63               int top=0;
 64               do
 65               {
 66                   top=q.top();q.pop();vis[to]=0;
 67                   v[cnt].ps(top);
 68               }
 69               while(to!=top);
 70               v[cnt].ps(x);
 71           }
 72       }  
 73       else 
 74           low[x]=min(low[x],dfn[to]);
 75    }
 76 }
 77 int n;
 78 int cut_kuan[MAXN];
 79 void init()
 80 {
 81     num_id=cnt;
 82     for(int i=1;i<=n;++i)
 83     {
 84         if(cut[i]==1)
 85         {
 86             belong[i]=++num_id;
 87             cut_kuan[num_id]=i;  
 88         }
 89     }
 90     for(int x=1;x<=cnt;++x)
 91     {
 92         for(int i=0;i<v[x].size();++i)
 93         {
 94             int now=v[x][i];
 95             if(cut[now]==1)
 96             {
 97                 add2(belong[now],x);
 98                 add2(x,belong[now]);
 99             }
100             else 
101             {
102                 belong[now]=x;
103             }
104         }
105     }
106 }
107 bool bian[MAXN];int fa[MAXN];
108 void DFS(int x)
109 {
110    bian[x]=1;
111    for(int i=head2[x];i;i=e2[i].n)
112    {
113        int to=e2[i].to;
114        if(bian[to]==1)continue;
115        fa[to]=x;
116        DFS(to);
117    }
118 }
119 int ans[MAXN];
120 void find()
121 {
122     int x=belong[n];
123     while(fa[x]!=0)
124     {
125         x=fa[x];
126         if(cut_kuan[x]!=0&&x!=belong[1])
127         {
128            ans[++ans[0]]=cut_kuan[x];
129         }
130     }
131 }
132 int T,m;
133 int main()
134 {
135     scanf("%d",&T);
136     while(T--)
137     {
138          memset(head1,0,sizeof(head1));
139          memset(head2,0,sizeof(head2));
140          memset(cut,0,sizeof(cut));
141          memset(dfn,0,sizeof(dfn));
142          memset(low,0,sizeof(low));
143          memset(vis,0,sizeof(vis));
144          memset(belong,0,sizeof(belong));
145          memset(fa,0,sizeof(fa));
146          memset(bian,0,sizeof(bian));
147          memset(ans,0,sizeof(ans));
148          memset(cut_kuan,0,sizeof(cut_kuan));
149          tot1=0;tot2=0;
150          n=read();m=read();
151          for(int i=1;i<=m;++i)
152          {
153              int x,y;
154              //scanf("%d%d",&x,&y);
155              x=read();y=read();
156              add1(x,y);add1(y,x); 
157          }
158          tarjan(1);
159          init();
160          DFS(belong[1]);
161          find();
162          printf("%d\n",ans[0]);
163          sort(ans+1,ans+ans[0]+1);
164          for(int i=1;i<=ans[0];++i)
165          {
166              printf("%d ",ans[i]);
167          }
168          cout<<endl;
169          for(int i=1;i<=cnt;++i)
170          {
171              v[i].clear();
172          }
 173           cnt = 0 ; out = 0 ; num_id = 0 ;
174      }
 175 }

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