tarjan缩点模板

#include<cstdio>
#include<stack>
#include<map>
using namespace std;
const int maxn=50010;
stack<int>q;
int head[maxn],nxt[maxn],to[maxn],tt;
int dfn[maxn],low[maxn];
int n,m,index,bcnt;
int belong[maxn];
bool vis[maxn];
int in[maxn],out[maxn];
//map<pair<int,int>,int>mp;
int min(int x,int y)
{
    return x>y?y:x;
}
int max(int x,int y)
{
    return x>y?x:y;
}
int read()
{
    int x=0,f=1;char ch=getchar();
    while (ch<'0' || ch>'9'){if (ch=='-') f=-1;ch=getchar();}
    while (ch>='0' && ch<='9'){x=x*10+ch-48;ch=getchar();}
    return x*f;
}
void add(int u,int v)
{
    to[++tt]=v;
    nxt[tt]=head[u];
    head[u]=tt;
}
void tarjan(int u)
{
    low[u]=dfn[u]=++index;
    q.push(u);vis[u]=1;
    for(int i=head[u];i;i=nxt[i])
    {
        int v=to[i];
        if(!dfn[v])
        {
            tarjan(v);
            low[u]=min(low[u],low[v]);
            //printf("%d\n",low[u]);
         }
        else if(vis[v])
        {
            low[u]=min(dfn[v],low[u]);
            //printf("%d\n",low[u]);
        }
    }
    if(low[u]==dfn[u])
    {
        int k;bcnt++;
        while(k!=u)
        {
            k=q.top();q.pop();
            vis[k]=0;
            belong[k]=bcnt;
        }
    }
}
int main()
{
    n=read();//m=read();
    for(int i=1;i<=n;i++)
    {
        while(true)
        {
            int tmp=read();
            //if(mp.count(make_pair(1,tmp))>0) continue;
            if(tmp!=0&&tmp!=i)
            {
                add(i,tmp);
                //mp[make_pair(i,tmp)]=1;
            }
            else if(tmp==0) break;
        }
    }
    for(int i=1;i<=n;i++)
    {
        if(!dfn[i]) tarjan(i);
    }
    for(int u=1;u<=n;u++)
        for(int i=head[u];i;i=nxt[i])
        {
            int v=to[i];
            if(belong[u]!=belong[v])
            {
                in[belong[v]]++;out[belong[u]]++;
            }
        }
    int t1=0,t2=0;
    for(int i=1;i<=bcnt;i++)
    {
        if(in[i]==0) t1++;
        if(out[i]==0) t2++;
    }    
    printf("%d\n",t1);
    if(bcnt==1)
    {
        printf("0");
    }
    else printf("%d",max(t1,t2));
    return 0;
 }