POJ 1236 Network of Schools tarjan强连通缩点

tarjan算法很犀利，不解释，不解释。。。

缩点然后判断度数

#include<iostream>
#include<vector>
#include<cstring>
#include<deque>
#include<string>
#include<cstdio>
#include<cstdlib>
#include<iomanip>
#include<algorithm>
#include<cassert>
#define pb push_back
using namespace std;

const int maxn = 111;

vector<int>g[maxn];
vector<int>v[maxn];
vector<int>s;
bool hash[maxn][maxn];
int be[maxn];
int dfn[maxn];
int low[maxn];
bool ins[maxn];
int n,df,nb;
int in[maxn];
int out[maxn];
int sa,sd;

void tarjan(int now)
{
    low[now] = dfn[now] = df++;
    s.pb(now);
    ins[now] = true;
    int to;
    for(int i=0;i<g[now].size();i++)
    {
        to = g[now][i];
        if(!dfn[to])
        {
            tarjan(to);
            low[now] = min(low[to],low[now]);
        }
        else if( ins[to] )
        {
            low[now] = min(low[to],low[now]);
        }
    }
    if(low[now] == dfn[now] )
    {
        while(s.back()!=now)
        {
            to = s.back();
            be[to] = nb;
            s.pop_back();
            ins[to] = false;
        }
        be[now] = nb++;
        ins[now] = false;
        s.pop_back();
    }
    return ;
}

void start()
{
    s.clear();
    nb = df = 1;
    memset(ins,false,sizeof(ins));
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(be,0,sizeof(be));
    memset(hash,false,sizeof(hash));
    memset(in,0,sizeof(in));
    memset(out,0,sizeof(out));
    for(int i=1;i<=n;i++)
    {
        if(!dfn[i])
        {
            tarjan(i);
        }
    }
  /*  for(int i=1;i<=n;i++)
    {
        cout<<"dfn["<<i<<"] == "<<dfn[i]<<endl;
        cout<<"low["<<i<<"] == "<<low[i]<<endl;
        cout<<"be["<<i<<"] == "<<be[i]<<endl;
    } */
    nb--;
    if(nb==1)
    {
        sa = 1;
        sd = 0;
        return ;
    }
    int from,to;
    for(int i=1;i<=n;i++)
    {
        from = be[i];
        for(int j=0;j<g[i].size();j++)
        {
            to = be[g[i][j]];
            if(from != to && !hash[from][to] )
            {
                hash[from][to] = true;
                v[from].pb(to);
            }
        }
    }
    for(int i=1;i<=nb;i++)
    {
        from = i;
        for(int j=0;j<v[i].size();j++)
        {
            to = v[i][j];
            out[from]++;
            in[to]++;
        }
    }
    sa = 0;
    sd = 0;
    for(int i=1;i<=nb;i++)
    {
        if(!in[i])
        {
            sa++;
        }
        if(!out[i])
        {
            sd++;
        }
    }
    sd = max(sa,sd);
    return ;
}

int main()
{
    while(cin>>n)
    {
        for(int i=1;i<=n;i++)
        {
            g[i].clear();
            v[i].clear();
        }
        int x;
        for(int i=1;i<=n;i++)
        {
            while(cin>>x)
            {
                if( !x )
                {
                    break;
                }
                g[i].push_back(x);
            }
        }
        start();
        cout<<sa<<endl<<sd<<endl;
    }
    return 0;
}