bzoj1123 BLO tarjan求点双连通分量

Posted 2020-10-02 Loser Of Life

填坑……链接：http://www.lydsy.com/JudgeOnline/problem.php?id=1123

题意：问切断第i个点之后多少对点不再联通。

就是个求割点同时计算出双连通分量大小嘛……

 1 #include<iostream>
 2 #include<cstdio>
 3 #include<cstring>
 4 #include<algorithm>
 5 using namespace std;
 6 const int maxn=100005,maxm=500005;
 7 struct node
 8 {
 9     int from,to,next;
10 }edge[maxm<<1];
11 int head[maxn],tot;
12 void addedge(int u,int v)
13 {
14     edge[++tot]=(node){u,v,head[u]};head[u]=tot;
15 }
16 int low[maxn],dfn[maxn],belong[maxn],cnt,bcnt,size[maxn],n,m;
17 bool iscut[maxn];
18 long long sum[maxn];
19 #include<vector>
20 #include<stack>
21 stack<node>s;vector<int>bcc[maxn];
22 void dfs(int root,int pa)
23 {
24     low[root]=dfn[root]=++cnt;
25     int son=0;size[root]=1;long long su=0;
26     for(int i=head[root];i;i=edge[i].next)
27     {
28         int v=edge[i].to;
29         if(!dfn[v])
30         {
31             s.push(edge[i]);son++;
32             dfs(v,root);low[root]=min(low[root],low[v]);
33             size[root]+=size[v];
34             if(low[v]>=dfn[root])
35             {
36                 sum[root]+=su*size[v];su+=1ll*size[v];
37                 iscut[root]=1;bcnt++;bcc[bcnt].clear();
38                 node x;int u=-1,va=-1;
39                 do
40                 {
41                     x=s.top();s.pop();
42                     u=edge[i].from,va=edge[i].to;
43                     if(belong[u]!=bcnt)bcc[bcnt].push_back(u),belong[u]=bcnt;
44                     if(belong[va]!=bcnt)bcc[bcnt].push_back(va),belong[va]=bcnt;
45                 }while(u!=root&&va!=v);
46             }
47         }
48         else if(dfn[v]<dfn[root]&&v!=pa)
49         {
50             s.push(edge[i]);
51             low[root]=min(low[root],dfn[v]);
52         }
53     }
54     if(pa<0&&son==1)iscut[root]=0;
55     sum[root]+=su*(n-su-1);
56 }
57 int haha()
58 {
59     scanf("%d%d",&n,&m);
60     for(int i=1;i<=m;i++)
61     {
62         int x,y;scanf("%d%d",&x,&y);
63         addedge(x,y);addedge(y,x);
64     }
65     for(int i=1;i<=n;i++)
66         if(!dfn[i])dfs(i,-1);
67     for(int i=1;i<=n;i++)printf("%lld\n",1ll*(sum[i]+n-1)*2);
68 }
69 int sb=haha();
70 int main(){;}

bzoj1123