poj 1523 SPF

求删掉割点后图变成几个连通分支。

求割点，对每个块上的点进行统计。输出割点存在于几个块就可以了。

#include <iostream>#include <cstdio>#include <vector>#include <cmath>#include <stack>#include <map>#include <set>#include <queue>#include <cstring>#include <algorithm>using namespace std;#define L(t) t<<1#define R(t) t<<1|1#define eps 1e-7typedef long long LL;const int INF=1000000010;const int maxn=1005;const int maxm=1005;const int MOD=1000000007;int head[maxn],next[maxn*3],to[maxn*3];int tot,cnt,top;int dfn[maxn],low[maxn],st[maxn];int block[maxn];bool isGe[maxn];bool node[maxn];void cutBlock(int v){    dfn[v]=low[v]=++cnt;    st[++top]=v;    int u;    for(int i=head[v];i!=-1;i=next[i])    {        u=to[i];        if(!dfn[u])        {            cutBlock(u);            low[v]=min(low[v],low[u]);            if(low[u]>=dfn[v])            {                isGe[v]=true;                while(true)                {                    block[st[top]]++;                    if(st[top--]==u)                        break;                }                block[v]++;            }        }        else        {            low[v]=min(low[v],dfn[u]);        }    }}void addEdge(int u,int v){    next[tot]=head[u],to[tot]=v,head[u]=tot++;    next[tot]=head[v],to[tot]=u,head[v]=tot++;}int main(){    //freopen("in.txt","r",stdin);    int u,v;    int T=0;    while(scanf("%d",&u),u)    {        cnt=0,tot=0;        memset(isGe,0,sizeof(isGe));        memset(block,0,sizeof(block));        memset(head,-1,sizeof(head));        memset(node,0,sizeof(node));        memset(dfn,0,sizeof(dfn));        scanf("%d",&v);        addEdge(u,v);        while(scanf("%d",&u),u)        {            scanf("%d",&v);            addEdge(u,v);            node[u]=1,node[v]=1;        }        printf("Network #%d\n",++T);        for(int i=1;i<maxn;i++)        {            top=0;            if(!dfn[i]&&node[i])            {                cutBlock(i);            }        }        bool pf=1;        for(int i=1;i<maxn;i++)        {            if(isGe[i]&&node[i]&&block[i]>1)            {                printf("  SPF node %d leaves %d subnets\n",i,block[i]);                pf=0;            }        }        if(pf)            printf("  No SPF nodes\n");        printf("\n");    }}