电厂计划

[Time Gate]

http://220.180.209.150:38888/problem/270

【解题思路】

Tarjan算法求割点、桥、缩点

【code】

#include <cstdio>
#include <cstring>
#include <iostream>
#include <algorithm>
using namespace std;
int n,m;
struct ENode{
    int u;
    int v;
    int w;
    int next;
}edge[50005];
int p[10005],cnt;
void Add(int u, int v){
    edge[++cnt].u=u; 
    edge[cnt].v=v;
    edge[cnt].next=p[u];
    p[u]=cnt;
}
int dfn[50005],cTime,low[50005];
int cut[50005]; 
void Tarjan(int u, int fa ){
    dfn[u]=low[u]=++cTime;        
    for(int i=p[u];i;i=edge[i].next){    
        int v=edge[i].v;
        if(v == fa)continue;
        if(!dfn[v]){
            Tarjan(v,u);
            low[u]=min(low[u],low[v]);     
            if(low[v]>=dfn[u]){        
                cut[u]++;        
            }
        }
        else     
            low[u]=min(low[u],dfn[v]);
    }
}
int main(){
    int x,y;
    while(1){
        int c=0,ans=-1;
        scanf("%d%d",&n,&m);
        if(!n&&!m)break;
        memset(edge,0,sizeof(edge));
        memset(p,0,sizeof(p));
        cnt=0;
        memset(dfn,0,sizeof(dfn));
        cTime=0;
        memset(low,0,sizeof(low));
        memset(cut,0,sizeof(cut));
        for(int i=0;i<m;i++){
            scanf("%d%d",&x,&y);
            Add(x+1,y+1);
            Add(y+1,x+1);    
        }
        for(int i=1;i<=n;i++)
            if(!dfn[i]){
                c++;
                cut[i]=-1;
                Tarjan(i,-1);
            }
        for(int i=1;i<=n;i++)
            if(cut[i]>ans)ans=cut[i];
        printf("%d\n",ans+c);
    }
    return 0;
}