POJ 1087 A Plug for UNIX

POJ 1087 A Plug for UNIX

这是本人AC的第一道网络流建模的题目哇～内牛满面！！！做了两天才AC……
网络流题目重在 构图。
以下是我的代码：

#include < iostream >
#include < string >
#include < queue >
#include < map >
#include < algorithm >
#include < cstdio >
#include < cstring >
using   namespace  std;
const   int  kMaxn( 507 );
const   int  kInf( 77777 );

int  a,b,c;
map < string , int >  r;
int  n,source,sink,maxflow,cap[kMaxn][kMaxn],flow[kMaxn][kMaxn];

void  SAP()
{
     int  d[kMaxn],num[kMaxn],p[kMaxn];

    memset(flow, 0 ,kMaxn * kMaxn * sizeof ( int ));
    memset(d, 0x7f ,kMaxn * sizeof ( int ));
    memset(num, 0 ,kMaxn * sizeof ( int ));
    queue < int >  q;
    d[sink] = 0 ;
    num[ 0 ] ++ ;
    q.push(sink);
     while ( ! q.empty())
    {
         int  v(q.front());q.pop();
         for ( int  u = 1 ;u <= n;u ++ )
             if (d[u] >= n  &&  cap[u][v] > flow[u][v])
            {
                d[u] = d[v] + 1 ;
                num[d[u]] ++ ;
                q.push(u);
            }
    }

    maxflow = 0 ;
     int  u(source),v;
     while (d[source] < n)
    {
        v =- 1 ;
         for ( int  i = 1 ;i <= n;i ++ )
             if (cap[u][i] > flow[u][i]  &&  d[u] == d[i] + 1 )
            {v = i; break ;}
         if (v !=- 1 )
        {
            p[v] = u;u = v;
             if (u == sink)
            {
                 int  add(kInf);
                 for (u = sink;u != source;u = p[u])
                    add = min(add,cap[p[u]][u] - flow[p[u]][u]);
                maxflow += add;
                 for (u = sink;u != source;u = p[u])
                {
                    flow[p[u]][u] += add;
                    flow[u][p[u]] -= add;
                }
            }
        }
         else
        {
            num[d[u]] -- ;
             if ( ! num[d[u]])
                 return ;
            d[u] = n;
             for (v = 1 ;v <= n;v ++ )
                 if (cap[u][v] > flow[u][v])
                    d[u] = min(d[u],d[v] + 1 );
            num[d[u]] ++ ;
             if (u != source)
                u = p[u];
        }
    }
}

int  main()
{
    source = 1 ;
    sink = 2 ;
    n = 2 ;
    memset(cap, 0 ,kMaxn * kMaxn * sizeof ( int ));

    cin >> a;
     for ( int  i = 1 ;i <= a;i ++ )
    {
         string  t;
        cin >> t;
        r[t] = ( ++ n);
        cap[n][sink] ++ ;
    }
    cin >> b;
     for ( int  i = 1 ;i <= b;i ++ )
    {
         string  t1,t2;
        cin >> t1 >> t2;
        r[t1] = ( ++ n);
        cap[source][n] ++ ;
         if ( ! r.count(t2))
            r[t2] = ( ++ n);
        cap[r[t1]][r[t2]] ++ ;
    }
    cin >> c;
     for ( int  i = 1 ;i <= c;i ++ )
    {
         string  t1,t2;
        cin >> t1 >> t2;
         if ( ! r.count(t1))
            r[t1] = ( ++ n);
         if ( ! r.count(t2))
            r[t2] = ( ++ n);
        cap[r[t1]][r[t2]] = kInf;
    }

    SAP();

    printf( " %d\n " ,b - maxflow);

     return   0 ;
}