poj 2186 Popular Cows

#include <iostream>
#include<string.h>
#include<stdio.h>
#include<stdlib.h>
using namespace std;
const int maxn=10001;
int n,m;
struct node
{
intto;
struct node*next;
}e1[maxn],e2[maxn],*p;

int edgeini(struct node e[])
{
for(inti=1;i<=n;i++) e[i].next=&e[i];
}

int edgemake(int from,int to,struct node e[])
{
p=(struct node *)malloc(sizeof(struct node));
p->next=e[from].next;
e[from].next=p;
p->to=to;
}

int min(int a,int b)
{
if(a<b) return(a);
return(b);
}

intlow[maxn],dfn[maxn],visit[maxn],text[maxn],stack[maxn],team[maxn];
int time,ret,top;
int tarjan(int u)
{
dfn[u]=++time;
low[u]=dfn[u];
visit[u]=1;
text[u]=1;
stack[++top]=u;

structnode *q;
q=e1[u].next;
while(q!=&e1[u])
{
if(!visit[q->to])
{
tarjan(q->to);
low[u]=min(low[u],low[q->to]);
}
else if(text[q->to])
{
low[u]=min(low[u],dfn[q->to]);
}
q=q->next;

}
if(dfn[u]==low[u])
{
ret++;
while(stack[top]!=u)
{
int v=stack[top];
team[v]=ret;
top--;
text[v]=0;

struct node *q;
q=e1[v].next;
while(q!=&e1[v])
{edgemake(u,q->to,e1);q=q->next;}
q=e2[v].next;
while(q!=&e2[v])
{edgemake(q->to,u,e1);q=q->next;}
}
team[stack[top]]=ret;
text[stack[top]]=0;
top--;
}
}

int countout(int u)
{
intans=0;
p=e1[u].next;
while(p!=&e1[u])
{
if(dfn[p->to]==low[p->to]&&p->to!=u)
ans++;
p=p->next;
}
return(ans);
}

int main()
{
scanf("%d%d",&n,&m);
edgeini(e1),edgeini(e2);
for(inti=1;i<=m;i++)
{
int from,to;
scanf("%d %d",&from,&to);
edgemake(from,to,e1);
edgemake(to,from,e2);
}

memset(text,0,sizeof(text));
memset(visit,0,sizeof(visit));
memset(team,0,sizeof(team));
memset(low,0,sizeof(low));
memset(dfn,0,sizeof(dfn));
time=0;
top=0;
ret=0;
for(inti=1;i<=n;i++)
if(!visit[i]) tarjan(i);

intsum=0,tmp;
for(inti=1;i<=n;i++)
if(low[i]==dfn[i])
if(!countout(i)) {sum++;tmp=i;}

if(sum>1) printf("0\n");
else
{
int ans=0;
for(int i=1;i<=n;i++)
if(team[i]==team[tmp])
ans++;
printf("%d\n",ans);
}

return0;
}