poj 1523 SPF 求割点以及删除该割点后联通块的数量

#include<stdio.h>
#include<string.h>
#include<iostream>
#include<algorithm>
using namespace std;
const int MAXN = 10010;
const int MAXM = 100010;
struct Edge
{
    int to,next;
    bool cut;//是否为桥的标记
} edge[MAXM];
int head[MAXN],tot;
int Low[MAXN],DFN[MAXN],Stack[MAXN];
int Index,top;
bool Instack[MAXN];
bool cut[MAXN];
int add_block[MAXN];//删除一个点后增加的连通块
int bridge;
void addedge(int u,int v)
{
    edge[tot].to = v;
    edge[tot].next = head[u];
    edge[tot].cut = false;
    head[u] = tot++;
}
void Tarjan(int u,int pre)
{
    int v;
    Low[u] = DFN[u] = ++Index;
    Stack[top++] = u;
    Instack[u] = true;
    int son = 0;
    for(int i = head[u]; i != -1; i = edge[i].next)
    {
        v = edge[i].to;
        if(v == pre)continue;
        if( !DFN[v] )
        {
            son++;
            Tarjan(v,u);
            if(Low[u] > Low[v])Low[u] = Low[v];
            if(Low[v] > DFN[u])
            {
                bridge++;
                edge[i].cut = true;
                edge[i^1].cut = true;
            }
            if(u != pre && Low[v] >= DFN[u])//不是树根
            {
                cut[u] = true;
                add_block[u]++;
            }
        }
        else if( Low[u] > DFN[v])
            Low[u] = DFN[v];
    }
//树根，分支数大于1
    if(u == pre && son > 1)
        cut[u] = true;
    if(u == pre)
        add_block[u] = son - 1;
    Instack[u] = false;
    top--;
}
void solve(int N)
{
    memset(DFN,0,sizeof(DFN));
    memset(Instack,0,sizeof(Instack));
    memset(add_block,0,sizeof(add_block));
    memset(cut,false,sizeof(cut));
    Index = top = 0;
    int cnt = 0;//原来的连通块数
    for(int i = 1; i <= N; i++)
        if( !DFN[i] )
        {
            Tarjan(i,i);//找割点调用必须是Tarjan(i,i)
            cnt++;
        }
    int ans = 0;
    bool flag=true;
    for(int i = 1; i <= N; i++){
            if(cut[i]==true){
                    flag=false;
            printf("  SPF node %d leaves %d subnets\n",i,add_block[i]+1);
            }
    }

    if(flag)
        printf("  No SPF nodes\n");
    puts("");
}
void init()
{
    tot = 0;
    memset(head,-1,sizeof(head));
}
int main()
{
    int n,m;
    int u,v;
    int cas=0;
    while(scanf("%d",&u)!=EOF)
    {
        cas++;
        if(u==0)
            break;
              init();
        scanf("%d",&v);
            addedge(u,v);
            addedge(v,u);
      n=max(u,v);
        while(scanf("%d",&u)!=EOF){
            if(u==0)
            break;
            scanf("%d",&v);
            addedge(u,v);
            addedge(v,u);
            int temp=max(u,v);
            n=max(temp,n);
        }
        printf("Network #%d\n",cas);
        solve(n);
    }
    return 0;
}