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_backusing 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;}