POJ 1236 Network of Schools 有向图强连通分量

参考这篇博客：

http://blog.csdn.net/ascii991/article/details/7466278

#include <stdio.h>
#include <string.h>
#include <algorithm>
#include <math.h>
#include <vector>
#include <stack>
using namespace std;
typedef long long LL;
const int N = 1e2+5;
int head[N],tot,p,h[N],n,out[N],in[N];
struct Edge{
   int u,v,next;
}edge[N*N],e[N*N];
void add(int u,int v){
   edge[tot].u=u;
   edge[tot].v=v;
   edge[tot].next=head[u];
   head[u]=tot++;
}
void addedge(int u,int v){
   e[p].v=v;
   e[p].next=h[u];
   h[u]=p++;
}
int clk,dfn[N],low[N],cnt,bel[N];
bool instack[N];
stack<int>s;
void targin(int u){
   dfn[u]=low[u]=++clk;
   s.push(u);
   instack[u]=true;
   for(int i=head[u];~i;i=edge[i].next){
      int v=edge[i].v;
      if(!dfn[v]){
         targin(v);
         low[u]=min(low[u],low[v]);
      }
      else if(instack[v])
        low[u]=min(low[u],dfn[v]);
   }
   if(dfn[u]==low[u]){
      ++cnt;
      int k;
      do{
        k=s.top();
        s.pop();
        instack[k]=false;
        bel[k]=cnt;
      }while(k!=u);
   } 
}
int main(){
    scanf("%d",&n);
    memset(head,-1,sizeof(head));
    memset(h,-1,sizeof(h));
    for(int i=1;i<=n;++i){
        for(int x;;){
           scanf("%d",&x);
           if(!x)break;
           add(i,x); 
        }
    }
    for(int i=1;i<=n;++i)
      if(!dfn[i])targin(i);
    if(cnt==1){
        printf("1
0
");
        return 0;
    }
    for(int i=0;i<tot;++i){
        int k1=bel[edge[i].u],k2=bel[edge[i].v];
        if(k1==k2)continue;
        addedge(k1,k2);
        ++in[k2];
        ++out[k1]; 
    }
    int ans1=0,ans2=0;
    for(int i=1;i<=cnt;++i){
      if(!in[i])++ans1;
      if(!out[i])++ans2;
    }
    printf("%d
%d
",ans1,max(ans1,ans2));
    return 0;
}