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\n",Case++);

        if(key[1]>=2)

        {

            printf("  SPF node %d leaves %d subnets\n",1,key[1]);

            flag=1;

        }

        if(!flag)

            printf("  No SPF nodes\n");

        else

        for(i=2;i<=1000;i++)

        {

            if(key[i])

                printf("  SPF node %d leaves %d subnets\n",i,key[i]+1);

        }

        printf("\n");

    }

    return 0;

}