poj 1523 求割点把一个图分成几个联通部分

#include<stdio.h>
#include<string.h>
#define N  1100
struct node {
int u,v,next;
}bian[N*N*2];
int head[N],dfn[N],low[N],index,cut[N],yong,visit[N],dd[N],len,vis[N];
void init() {
memset(head,-1,sizeof(head));
memset(dfn,0,sizeof(dfn));
memset(low,0,sizeof(low));
memset(cut,0,sizeof(cut));
index=0;yong=0;
memset(visit,0,sizeof(visit));
}
int Min(int a,int b) {
return a>b?b:a;
}
void addedge(int u,int v) {
bian[yong].u=u;
bian[yong].v=v;
bian[yong].next=head[u];
head[u]=yong++;
}
void tarjan(int u,int pre) {
dfn[u]=low[u]=++index;
int i;
for(i=head[u];i!=-1;i=bian[i].next) {
    int v=bian[i].v;
    if(!dfn[v]) {
        tarjan(v,u);
        low[u]=Min(low[u],low[v]);
        if(low[v]>=dfn[u])
            cut[u]++;
    }
    else
        low[u]=Min(low[u],dfn[v]);
}
if(pre<0)
    cut[u]--;
}
int main() {
    int a,b,i,j,in=0,flag;
     while(scanf("%d",&a),a) {
            scanf("%d",&b);
            init();
            addedge(a,b);
            addedge(b,a);
     visit[a]=visit[b]=1;
        while(scanf("%d",&a),a) {
            scanf("%d",&b);
            addedge(a,b);
            addedge(b,a);
                 visit[a]=visit[b]=1;
        }
        printf("Network #%d\n",++in);
        flag=0;
        for(i=1;i<=1000;i++)
        if(!dfn[i]&&visit[i])
            tarjan(i,-1);
        for(i=1;i<=1000;i++)
            if(visit[i]&&cut[i])
                if(cut[i]+1>0) {
                    printf("  SPF node %d leaves %d subnets\n",i,cut[i]+1);
                flag=1;
                }
        if(flag==0)
            printf("  No SPF nodes\n");
        printf("\n");
     }
return 0;
}