bzoj1393 旅游航道

#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cstdlib>
#define MAXN 150010
#define REP(i,k,n) for(int i=k;i<=n;i++)
#define in(a) a=read()
using namespace std;
inline int read(){
    int f=1,x=0;
    char ch=getchar();
    for(;!isdigit(ch);ch=getchar())
        if(ch==‘-‘)
            f=-1;
    for(;isdigit(ch);ch=getchar())
        x=x*10+ch-‘0‘;
    return x*f;
}
int n,m,cnt,ans;
int dfn[MAXN],low[MAXN];
int total=0,head[MAXN],nxt[MAXN<<1],to[MAXN<<1];
inline void adl(int a,int b){
    total++;
    to[total]=b;
    nxt[total]=head[a];
    head[a]=total;
    return ;
}
inline void tarjan(int u,int f){
    low[u]=dfn[u]=++cnt;
    for(int e=head[u];e;e=nxt[e]){
        if(!dfn[to[e]] && to[e]!=f){
            tarjan(to[e],u);
            low[u]=min(low[to[e]],low[u]);
            if(low[to[e]]>dfn[u])  ans++;
        }
        else  if(dfn[to[e]]<low[u] && to[e]!=f)  low[u]=dfn[to[e]];
    }
    return ;
}
int main(){
    while(scanf("%d%d",&n,&m)!=EOF){
        if(n==0 && m==0)  return 0;
        total=0;
        memset(dfn,0,sizeof(dfn));
        memset(low,0,sizeof(low));
        memset(head,0,sizeof(head));
        cnt=ans=0;
        int a,b;
        REP(i,1,m){
            in(a);in(b);
            adl(a,b);
            adl(b,a);
        }
        tarjan(1,0);
        cout<<ans<<endl; 
    }
}