poj 3177 Redundant Paths 边双连通

#include <iostream>
using namespace std;
#define MAXV 5010
#define min(a,b) (a>b?b:a)

int n,m;
bool map[MAXV][MAXV];
bool vis[MAXV];
int low[MAXV],dfn[MAXV];
int count;
int cnt[MAXV];

void init(){
memset(vis,0,sizeof(vis));
memset(low,0,sizeof(low));
memset(dfn,0,sizeof(dfn));
count=0;
}

void dfs(int x,int pre){
int i;
vis[x]=1;
low[x]=dfn[x]=++count;
for(i=1;i<=n;i++){
if(map[x][i]){
if(!vis[i]){
dfs(i,x);
low[x]=min(low[x],low[i]);
}
if(vis[i]==1 && i!=pre){
low[x]=min(low[x],dfn[i]);
}
}
}
}

int main(){
int a,b;
int i,j;
while(~scanf("%d%d",&n,&m)){
memset(map,0,sizeof(map));
while(m--){
scanf("%d%d",&a,&b);
map[a][b]=map[b][a]=1;
}

init();
dfs(1,1);

memset(cnt,0,sizeof(cnt));
for(i=1;i<=n;i++){					//计算每个点的度
for(j=1;j<=n;j++)
if(map[i][j]){
if(low[i]!=low[j]){
cnt[low[j]]++;
}
}
}
int ans=0;				//计算度为1的点的个数
for(i=1;i<=n;i++){
if(cnt[i]==1) ans++;
}
printf("%d\n",(ans+1)/2);
}
return 0;
}