poj 1236 Network of Schools

#include <cstdio>
#include <cstring> 
#include <algorithm>
#include <stack>
#include <vector>
using namespace std;
int n,dfn[110],low[110],scc[110],scc_cnt,dfs_clock,inx[110],outx[110],a,b;
stack<int> s;
vector<int> G[110];

void dfs(int u){
	dfn[u]=low[u]=++dfs_clock;
	s.push(u);
	for(int i=0;i<G[u].size();i++){
		int v=G[u][i];
		if(!dfn[v]){
			dfs(v);
			low[u]=min(low[u],low[v]);
		}
		else if(!scc[v])low[u]=min(low[u],dfn[v]);
	}
	if(dfn[u]==low[u]){
		scc_cnt++;
		for(;;){
			int x=s.top(); s.pop();
			scc[x]=scc_cnt;
			if(x==u)break;
		}
	}
}

int main(){
	while(scanf("%d",&n)!=EOF){
		dfs_clock=scc_cnt=a=b=0;
		for(int i=1;i<=n;i++)G[i].clear();
		memset(dfn,0,sizeof(dfn));
		memset(scc,0,sizeof(scc));
		memset(inx,0,sizeof(inx));
		memset(outx,0,sizeof(outx));
		for(int u=1;u<=n;u++){
			int v;
			while(scanf("%d",&v) && v!=0){
				G[u].push_back(v);
			}
		}
		for(int i=1;i<=n;i++)if(!scc[i])dfs(i);
		for(int u=1;u<=n;u++)
			for(int i=0;i<G[u].size();i++){
				int v=G[u][i];
				if(scc[u]!=scc[v]){inx[scc[v]]++; outx[scc[u]]++;}
			}
		for(int u=1;u<=scc_cnt;u++){
			if(!inx[u])a++;
			if(!outx[u])b++;
		}
		printf("%d
",a);
		if(scc_cnt==1)puts("0");
		else printf("%d
",max(a,b));
	}
	return 0;
}