POJ 1149 PIGS

POJ 1149 PIGS

网络流最大流问题。将顾客看做结点，另外增加一个源点和汇点，构图方式如下：源点和每个猪圈的第一个顾客连边，权值为初始时猪圈中猪的数目；每个顾客和汇点连一条边，权值为希望购买的猪的数目；如果顾客j紧跟着顾客i打开某个猪圈，那么结点i和结点j之间连一条边，权值为kInf。
以下是我的代码：

#include < queue >
#include < algorithm >
#include < cstdio >
#include < cstring >
using   namespace  std;
const   int  kMaxn( 107 );
const   int  kMaxpig( 1007 );
const   int  kInf( 0x7f7f7f7f );

int  pig,custom,r[kMaxpig],last[kMaxpig];
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()
{
    scanf( " %d%d " , & pig, & custom);
    source = custom + 1 ;
    sink = custom + 2 ;
    n = custom + 2 ;
    memset(cap, 0 ,kMaxn * kMaxn * sizeof ( int ));
     for ( int  i = 1 ;i <= pig;i ++ )
        scanf( " %d " , & r[i]);
    memset(last, 0 ,kMaxpig * sizeof ( int ));
     for ( int  i = 1 ;i <= custom;i ++ )
    {
         int  a,b;
        scanf( " %d " , & a);
         for ( int  j = 1 ;j <= a;j ++ )
        {
             int  t;
            scanf( " %d " , & t);
             if (last[t] == 0 )
            {
                last[t] = i;
                cap[source][i] += r[t];
            }
             else
            {
                cap[last[t]][i] = kInf;
                last[t] = i;
            }
        }
        scanf( " %d " , & b);
        cap[i][sink] += b;
    }

    SAP();

    printf( " %d\n " ,maxflow);

     return   0 ;
}