POJ1144 Network（判断割点）

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判断割点的个数
#include <iostream>#include <cstdlib>#include <cstdio>#include <cstring>#include <queue>#include <algorithm>const int N = 210;const int maxn = 500;const int maxm = 21010;const int inf = 1e8;#define MIN INT_MIN#define MAX 1e6#define LL long long#define init(a) memset(a,0,sizeof(a))#define FOR(i,a,b) for(int i = a;i<b;i++)#define max(a,b) (a>b)?(a):(b)#define min(a,b) (a>b)?(b):(a)using namespace std;int DFN[maxn],low[maxn],head[maxn];bool dian[maxn];int bianhao,n,bnum,root,vis[maxn];int gedian[maxn],ge;struct edge{    int v,next;}edge[maxm];void add(int u,int v){    edge[bnum].v=v;    edge[bnum].next=head[u];    head[u]=bnum++;}void tarjan(int u,int father)//判定割点{    int son=0;    vis[u]=1;//标记    DFN[u]=low[u]=bianhao++;    for(int i=head[u];i!=-1;i=edge[i].next)    {        int v=edge[i].v;        if(vis[v]==1 && v!=father)            low[u]=min(low[u],DFN[v]);        if(vis[v]==0)        {            tarjan(v,u);            son++;            low[u]=min(low[u],low[v]);            if((u==root && son>1 ) || (u!=root && DFN[u]<=low[v]))//判定割点的条件            {               dian[u]=1;            }        }    }    vis[u]=2;//去掉}void initt(){        memset(head,-1,sizeof(head));        init(DFN);init(low);        init(vis);init(dian);        bnum=0;bianhao = 1;//ge = 0;}int main(){    int a,b;    while(scanf("%d",&n),n)    {        initt();        while(scanf("%d",&a),a)        {            while(getchar()!='\n')            {                scanf("%d",&b);                add(a,b);                add(b,a);            }        }        root=1;        tarjan(1,-1);        int ans = 0;        FOR(i,1,n+1)        {            if(dian[i]!=0)            {                ans++;               // gedian[ge++] = i;            }        }        cout<<ans<<endl;       // puts("割点是");      /* printf("ge = %d\n",ge);        FOR(i,0,ge)        printf("%d ",gedian[i]);        printf("\n");*/    }    return 0;}
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