poj 1523 spf 求割点

来源：互联网发布：微电影拍摄知乎编辑：程序博客网时间：2024/05/16 14:05

无向图求割点的模版题。就是对tarjan的运用。

#include <iostream>#include <cstdio>#include <cstring>using namespace std;const int maxn=1e3+9,N=1e3;bool e[maxn][maxn];int dfn[maxn],low[maxn],count,in[maxn];void tarjan(int t,int from){    dfn[t]=low[t]=++count;    int ret=0;    for(int i=1;i<=N;i++)    if(e[t][i])    {        if(i==from) continue;        if(dfn[i]==-1)        {            ret++;            tarjan(i,t);            low[t]=min(low[t],low[i]);            if(low[i]>=dfn[t])            in[t]++;        }        else        {            low[t]=min(low[t],dfn[i]);        }    }    if(t==from)    in[t]=ret-1;}int main(){//    freopen("in.txt","r",stdin);    int from,to,tcase=0;    while(scanf("%d",&from),from)    {        scanf("%d",&to);        e[from][to]=1;        e[to][from]=1;        while(scanf("%d",&from),from)        {            scanf("%d",&to);            e[from][to]=1;            e[to][from]=1;        }//        printf("hi");        count=0;        memset(dfn,-1,sizeof(dfn));        memset(in,0,sizeof(in));        for(int i=1;i<=N;i++)        if(dfn[i]==-1)        tarjan(i,i);        printf("Network #%d\n",++tcase);        int cnt=0;        for(int i=1;i<=N;i++)        {            if(in[i]>0)            {                printf("  SPF node %d leaves %d subnets\n",i,in[i]+1);                cnt++;            }        }        if(!cnt)        printf("  No SPF nodes\n");        memset(e,0,sizeof(e));        printf("\n");    }    return 0;}