POJ 1523

无向图求割点模板题

#include <iostream>
#include <cstdio>
#include <string.h>
using namespace std;
const int N=1002;

int subnets[N];
int dfn[N],low[N];
int count,mun,son,ks;

bool map[N][N];
bool vis[N];

void init(){
    memset(map,0,sizeof(map));
    for(int i=0;i<=N;++i){
        vis[i]=dfn[i]=low[i]=subnets[i]=0;
    }
    count=1,son=0;
    mun=0;
    dfn[1]=low[1]=vis[1]=1;
}
void dfs(int x){
    for(int i=1;i<=mun;i++){
        if(map[x][i]){
            if(!vis[i]){
                vis[i]=1;
                dfn[i]=low[i]=++count;
                dfs(i);
                low[x]=min(low[x],low[i]);
                if(low[i]>=dfn[x]){
                    if(x==1)son++;
                    else subnets[x]++;
                }
            }
            else low[x]=min(low[x],dfn[i]);
        }
    }
}
void print(){
    bool yes=0;
    if(son>1)subnets[1]=son-1;
    printf("Network #%d
",++ks);
    for(int i=1;i<=mun;i++){
        if(subnets[i]){
            yes=1;
            printf("  SPF node %d leaves %d subnets
",i,subnets[i]+1);
        }
    }
    if(!yes)printf("  No SPF nodes
");
    printf("
");
}
int main(){
    //freopen("test.txt","r",stdin);
    int a,b;
    ks=0;
    while(scanf("%d",&a)&&a){
        init();
        scanf("%d",&b);
        map[a][b]=map[b][a]=1;
        mun=max(max(b,a),mun);
        while(scanf("%d",&a)&&a){
            scanf("%d",&b);
            map[a][b]=map[b][a]=1;
            mun=max(max(b,a),mun);
        }
        dfs(1);
        print();
    }
    return 0;
}