POJ 1523 SPF 割点

 1 #include<stdio.h>
 2 #include<string.h>
 3 
 4 #define N 1010
 5 #define M N*N
 6 
 7 int low[N],dfn[N],sub[N],index;
 8 int tail[N],eNum;
 9 struct Edge
10 {
11     int e,next;
12 }edge[M];
13 
14 int Min(int x,int y)
15 {
16     if(x>y)return y;
17     return x;
18 }
19 int Max(int x,int y)
20 {
21     if(x>y)return x;
22     return y;
23 }
24 void Add(int x,int y)
25 {
26     edge[eNum].e=y;
27     edge[eNum].next=tail[x];
28     tail[x]=eNum++;
29 
30     edge[eNum].e=x;
31     edge[eNum].next=tail[y];
32     tail[y]=eNum++;
33 }
34 void Build()
35 {
36     eNum=1;index=0;
37     memset(tail,-1,sizeof(tail));
38     memset(dfn,-1,sizeof(tail));
39     for(int i=1;i<=N;i++)
40         sub[i]=1;
41     sub[1]=0;
42 }
43 void Tarjan(int u)
44 {
45     int v;
46     dfn[u]=low[u]=++index;
47     for(int i=tail[u];i!=-1;i=edge[i].next)
48     {
49         v=edge[i].e;
50         if(dfn[v]==-1)
51         {
52             Tarjan(v);
53             low[u]=Min(low[u],low[v]);
54             if(dfn[u]<=low[v])
55                 sub[u]++;
56         }
57         else low[u]=Min(low[u],dfn[v]);
58     }
59 }
60 int main()
61 {
62     int x,y,n,cas=1;
63     while(scanf("%d",&x),x)
64     {
65         int flag=0;n=0;
66         Build();
67         scanf("%d",&y);
68         Add(x,y);
69         n=Max(n,Max(x,y));
70         while(1)
71         {
72             scanf("%d",&x);
73             if(x==0)break;
74             scanf("%d",&y);
75             Add(x,y);
76             n=Max(n,Max(x,y));
77         }
78         Tarjan(1);
79         printf("Network #%d\n",cas++);
80         for(int i=1;i<=n;i++)
81         {
82             if(sub[i]>1)
83             {
84                 flag=1;
85                 printf("  SPF node %d leaves %d subnets\n",i,sub[i]);
86             }
87         }
88         if(flag==0)
89             printf("  No SPF nodes\n");
90         printf("\n");
91     }
92     return 0;
93