【UVA10765】Doves and bombs （BCC求割点后联通块数量）

 1 #include<cstdio>
 2 #include<cstdlib>
 3 #include<cstring>
 4 #include<iostream>
 5 #include<algorithm>
 6 using namespace std;
 7 #define Maxn 10010
 8 
 9 int n,m;
10 int first[Maxn],low[Maxn],dfn[Maxn],fa[Maxn],son[Maxn];
11 int cut[Maxn];
12 int cnt;
13 
14 struct node
15 {
16     int x,y,next;
17 };
18 node t[Maxn*10],ans[Maxn];
19 int len;
20 
21 int mymin(int x,int y) {return x<y?x:y;}
22 
23 void ins(int x,int y)
24 {
25     t[++len].x=x;t[len].y=y;
26     t[len].next=first[x];first[x]=len;
27 }
28 
29 bool cmp(node x,node y) {return (x.x==y.x)?(x.y<y.y):(x.x>y.x);}
30 
31 void ffind(int x,int f)
32 {
33     dfn[x]=low[x]=++cnt;
34     fa[x]=f;
35     for(int i=first[x];i;i=t[i].next) if(t[i].y!=f)
36     {
37         int y=t[i].y;
38         if(dfn[y]==0)
39         {
40             ffind(y,x);
41             son[x]++;
42             low[x]=mymin(low[x],low[y]);
43             if(low[y]>=dfn[x]) cut[x]++;
44         }
45         else low[x]=mymin(low[x],dfn[y]);
46     }
47 }
48 
49 int main()
50 {
51     while(1)
52     {
53         scanf("%d%d",&n,&m);
54         if(n==0&&m==0) break;
55         len=0;cnt=0;
56         memset(first,0,sizeof(first));
57         while(1)
58         {
59             int a,b;
60             scanf("%d%d",&a,&b);
61             if(a==-1&&b==-1) break;
62             a++;b++;
63             ins(a,b);ins(b,a);
64         }
65         memset(dfn,0,sizeof(dfn));
66         memset(cut,0,sizeof(cut));
67         memset(son,0,sizeof(son));
68         ffind(1,0);ans[1].y=0;
69         if(son[1]>1) ans[1].x=son[1];
70         else ans[1].x=1;
71         for(int i=2;i<=n;i++)
72         {
73             ans[i].y=i-1;
74             ans[i].x=cut[i]+1;
75         }
76         sort(ans+1,ans+1+n,cmp);
77         for(int i=1;i<=m;i++) printf("%d %d\n",ans[i].y,ans[i].x);
78         printf("\n");
79     }
80     return 0;
81 }