poj1236 Network of Schools 强连通分量

 

#include<cstdio>
#include<algorithm>
#include<vector>
#include<cstring>
#include<stack>
using namespace std;

const int maxn = 100 + 10;

vector<int> G[maxn], G2[maxn];
vector<int> S;
int vis[maxn], sccno[maxn], scc_cnt;
int in[maxn],out[maxn];

int max(int a,int b)
{
	if(a>b) return a;
	else return b;
}
void dfs1(int u) 
{
    if(vis[u]) return;
    vis[u] = 1;
    for(int i = 0; i < G[u].size(); i++) dfs1(G[u][i]);
    S.push_back(u);
}

void dfs2(int u) 
{
    if(sccno[u]) return;
    sccno[u] = scc_cnt;
    for(int i = 0; i < G2[u].size(); i++) dfs2(G2[u][i]);
}

void find_scc(int n) 
{
	int i;
    scc_cnt = 0;
    S.clear();
    memset(sccno, 0, sizeof(sccno));
    memset(vis, 0, sizeof(vis));
    for(i = 0; i < n; i++) dfs1(i);
    for(i = n-1; i >= 0; i--)
    if(!sccno[S[i]]) { scc_cnt++; dfs2(S[i]); }
}
int main()
{
	int n,i,j;
	int u,v;
	while(scanf("%d",&n)!=EOF)
	{
		for(i=0;i<n;i++)
		{
			G[i].clear();
			G2[i].clear();
		}
		for(i=0;i<n;i++)
		{
			u=i;
			while(scanf("%d",&v),v!=0)
			{
				v--;
				G[u].push_back(v);
				G2[v].push_back(u);
			}
		}
		find_scc(n);
		for(i=0;i<n;i++)
		{
			for(j=0;j<G[u].size();j++)
			{
				u=G[u][j];
				if(sccno[i]!=sccno[u])
				{
					out[sccno[i]]++;
					in[sccno[u]]++;
				}
			}
		}
		for(i = 1; i <= scc_cnt; i++) in[i]=out[i]=1;
		for(u = 0; u < n; u++)
			for(i = 0; i < G[u].size(); i++) 
			{
				v = G[u][i];
				if(sccno[u] != sccno[v]) in[sccno[v]] = out[sccno[u]] = 0;
			}
		int a = 0, b = 0;
		for(i = 1; i <= scc_cnt; i++) 
		{
			if(in[i]) a++;
			if(out[i]) b++;
		}
		if(scc_cnt==1) printf("%d\n%d\n",1,0);
		else printf("%d\n%d\n",a,max(a,b));
	}
	return 0;
}