poj1236 Network of Schools【强连通分量（tarjan）缩点】

#include <vector>
#include <cstdio>
#include <cstring>
using namespace std;
#define MAXN 110
#define PB(X) push_back(X)
#define REP(X,N) for(int X=0;X<N;X++)
#define CLR(A,X) memset(A,X,sizeof(A))
typedef vector<int> VI;

int V,nV;
VI G[MAXN],nG[MAXN];
int low[MAXN],dfn[MAXN],st[MAXN],belong[MAXN];
int top,cnt,index;
bool inst[MAXN];
int ind[MAXN],outd[MAXN];

void init()
{
    top=cnt=index=0;
    CLR(dfn,0);
    CLR(ind,0);CLR(dfn,0);
}

void tarjan(int u)
{
    low[u]=dfn[u]=++index;
    st[top++]=u;
    inst[u]=1;
    REP(i,G[u].size())
    {
        int v=G[u][i];
        if(!dfn[v])
        {
            tarjan(v);
            if(low[v]<low[u])
                low[u]=low[v];
        }
        else if(inst[v] && dfn[v]<low[u])
            low[u]=dfn[v];
    }
    int j;
    if(low[u]==dfn[u])
    {
        cnt++;
        do
        {
            j=st[--top];
            inst[j]=0;
            belong[j]=cnt-1;
        }while(j!=u);
    }
}

int main()
{
    init();
    scanf("%d",&V);
    REP(i,V)
    {
        int x;
        while(scanf("%d",&x))
        {
            if(x==0)
                break;
            x--;
            G[i].PB(x);
        }
    }
    REP(i,V)
        if(!dfn[i])
            tarjan(i);
    nV=cnt;
    if(nV==1)
    {
        printf("1\n0\n");
        return 0;
    }
    REP(i,V)
    {
        REP(j,G[i].size())
        {
            int x=belong[i],y=belong[G[i][j]];
            if(x!=y)
            {
                nG[x].PB(y);
                ind[y]++;outd[x]++;
            }
        }
    }
    int noInd=0,noOutd=0;
    REP(i,nV)
    {
        if(!ind[i])
            noInd++;
        if(!outd[i])
            noOutd++;
    }
    printf("%d\n%d\n",noInd,max(noInd,noOutd));
    return 0;
}