poj 1523 求割点

思路：对于所有节点，每次找的子树，key[root]++;输出时，对于根节点就输出key[root]，对于其它节点i,输出key[i]+1;

#include<iostream>
#include<cstring>
#include<cstdio>
#include<algorithm>
#include<queue>
#define Maxn 1010
#define Maxm Maxn*10
#define inf 0x7fffffff
using namespace std;
int dfn[Maxn],low[Maxn],index[Maxn],vi[Maxn],n,e,lab,key[Maxn],flag=0;
struct Edge{
    int to,next,val,from;
}edge[Maxm];
void init()
{
    memset(dfn,0,sizeof(dfn));
    memset(key,0,sizeof(key));
    for(int i=1;i<=Maxn-1;i++)
        low[i]=inf;
    memset(index,-1,sizeof(index));
    memset(vi,0,sizeof(vi));
    e=lab=flag=0;
}
void addedge(int from, int to)
{
    edge[e].from=from;
    edge[e].to=to;
    edge[e].next=index[from];
    index[from]=e++;
    edge[e].to=from;
    edge[e].from=to;
    edge[e].next=index[to];
    index[to]=e++;
}
void dfs(int u)
{
    dfn[u]=lab++;
    vi[u]=1;
    int i,temp;
    for(i=index[u];i!=-1;i=edge[i].next)
    {
        temp=edge[i].to;
        if(!vi[temp])
            dfs(temp);
    }
}
void find(int u)
{
    int i,j,temp;
    vi[u]=1;
    for(i=index[u];i!=-1;i=edge[i].next)
    {
        int temp=edge[i].to;
        if(!vi[temp])
        {
            find(temp);
            if(low[temp]>=dfn[u])
            {
                key[u]++;
                flag=1;
            }
            low[u]=min(low[temp],low[u]);
            low[u]=min(low[u],dfn[u]);
        }
        
        low[u]=min(low[u],dfn[temp]);
    }
}
int main()
{
    int i,j,m,a,b,Case=1;
    while(scanf("%d",&a),a)
    {
        init();
        scanf("%d",&b);
        addedge(a,b);
        while(scanf("%d",&a),a)
        {
            scanf("%d",&b);
            addedge(a,b);
        }
        dfs(1);
        memset(vi,0,sizeof(vi));
        vi[1]=1;
        for(i=index[1];i!=-1;i=edge[i].next)
        {
            int temp=edge[i].to;
            if(!vi[temp])
            {
                find(temp);
                key[1]++;
            }
        }
        printf("Network #%d
",Case++);
        if(key[1]>=2)
        {
            printf("  SPF node %d leaves %d subnets
",1,key[1]);
            flag=1;
        }
        if(!flag)
            printf("  No SPF nodes
");
        else
        for(i=2;i<=1000;i++)
        {
            if(key[i])
                printf("  SPF node %d leaves %d subnets
",i,key[i]+1);
        }
        printf("
");
    }
    return 0;
}