POJ 1523 SPF 割点 Tarjan

#include<iostream>
#include<cstdio>
#include<queue>
#include<algorithm>
#include<cstring>
#include<string>
using namespace std;
typedef long long LL;
#define MAXN 1009
#define N 100
/*
求割点的个数 和割点被去掉之后联通快的个数
//删除割点u产生的连通数目为:u所在的连通分量数目+与u所连接的割边的数目+1(边:fa->u)
*/
struct edge
{
    //edge(int _t,int _next):to(_t),next(_next){}
    int to, next;
};
edge E[MAXN * MAXN];
int index, dfn[MAXN], low[MAXN], s[MAXN], head[MAXN], cnt, Max, cas = 1, root;
bool flag;
void Init()
{
    index = 0;
    Max = -1;
    cnt = 0;
    flag = false;
    memset(head, -1, sizeof(head));
    memset(dfn, 0, sizeof(dfn));
    memset(s, 0, sizeof(s));
    memset(low, 0, sizeof(low));
}
void add_edge(int u, int v)
{
    E[cnt].to = v;
    E[cnt].next = head[u];
    head[u] = cnt++;
    Max = max(max(u, v), Max);
}

void tarjan(int pre, int u)
{
    int son = 0;
    low[u] = dfn[u] = ++index;
    for (int i = head[u]; i != -1; i = E[i].next)
    {
        int v = E[i].to;
        if (!dfn[v])
        {
            tarjan(u, v);
            son++;
            low[u] = min(low[v], low[u]);
            if ((u == root&&son > 1) || (u != root&&low[v] >= dfn[u]))
            {
                flag = true;
                s[u]++;
            }
        }
        else if (v != pre)
            low[u] = min(low[u], dfn[v]);
    }
}

int main()
{
    int f, t;
    while (1)
    {
        Init();
        while (scanf("%d",&f), f)
        {
            scanf("%d", &t);
            add_edge(f, t);
            add_edge(t, f);
        }
        if (Max == -1)
            break;
        root = Max;
        tarjan(-1, Max);
        printf("Network #%d\n",cas++);
        if (!flag)
        {
            printf("  No SPF nodes\n");
        }
        else
        {
            for (int i = 1; i <= Max; i++)
                if (s[i] > 0)
                    printf("  SPF node %d leaves %d subnets\n", i, s[i] + 1);
        }
        printf("\n");
    }
}