POJ 2195 最小费用最大流

/* **********************************************************************
2分图最佳匹配，用的最小费用流
SPFA求增广路径，倒序追踪更新流，在Edmonds_karp算法的基础上修改。
需要注意结点的编号，man是从1~n，house是n+1~2*n，附加源点和汇点的容量
和权值分别为1和0。
需要注意的细节很多
********************************************************************** */
#include < iostream >
#include < queue >
using   namespace  std;
queue < int > q;
bool  flag[ 220 ]; // 标记是否出队
char  m[ 220 ][ 220 ]; // 地图
int  r,c,s,t;
struct  MAP
{
     int  c,f,w;
}map[ 220 ][ 220 ];
int  maxflow,mincost,nm,nh,man[ 101 ][ 2 ],house[ 101 ][ 2 ],v[ 220 ],pre[ 220 ],cost[ 220 ];
// cost[]----费用,pre[]----父节点
void  Init() // 构造网络流
{
     int  i,j;
    s = 2 * nh + 2 ,t = 2 * nh + 1 ;
     for (i = 1 ;i <= nm;i ++ )
    {
         for (j = 1 ;j <= nh;j ++ )
        {
            map[i][nm + j].c = 1 ;
            map[i][nm + j].w = abs(man[i][ 0 ] - house[j][ 0 ]) + abs(man[i][ 1 ] - house[j][ 1 ]);
        }
    }
     for (i = 1 ;i <= nm;i ++ )
    {
        map[s][i].c = 1 ; // nh+2为附加源点,nh+1为附加汇点
        map[s][i].w = 0 ;
    }
     for (i = nh + 1 ;i <= 2 * nh;i ++ )
    {
        map[i][t].c = 1 ;
        map[i][t].w = 0 ;
    }
     return  ;
}
bool  spfa()
{
     int  i,j;
    memset(v, 0 , sizeof (v));
    memset(flag, 0 , sizeof (flag));
    memset(pre, 0 , sizeof (pre));
     for (i = 1 ;i <= 2 * nh + 2 ;i ++ )
    {
        cost[i] = INT_MAX;
    }
     while ( ! q.empty())
        q.pop();
    v[s] = INT_MAX;
    pre[s] = s;
    cost[s] = 0 ;
    flag[s] = 1 ;
    q.push(s);
     while ( ! q.empty())
    {
        i = q.front();
         for (j = 1 ;j <= 2 * nh + 2 ;j ++ )
        {
             if (map[i][j].f < map[i][j].c && cost[i] + map[i][j].w < cost[j])
            {
                cost[j] = cost[i] + map[i][j].w;
                v[j] = min(v[i],map[i][j].c - map[i][j].f);
                pre[j] = i;
                 if ( ! flag[j])
                {
                    flag[j] = 1 ;
                    q.push(j);
                }
            }
             else   if (map[j][i].f && cost[i] - map[j][i].w < cost[j])
            {
                cost[j] = cost[i] - map[j][i].w;
                v[j] = min(v[i],map[j][i].f);
                pre[j] =- 1 * i;
                 if ( ! flag[j])
                {
                    flag[j] = 1 ;
                    q.push(j);
                }
            }
        }
        q.pop();
        flag[i] = 0 ;
    }
     if (v[t] > 0 )
         return   1 ;
     else  
         return   0 ;
}
int  mcmf()
{
     int  i,j;
    maxflow = 0 ,mincost = 0 ;
     while (spfa())
    {
        j = t;
        maxflow += v[t];
         while (j != s)
        {
            i = abs(pre[j]);
             if (pre[j] > 0 )
            {
                map[i][j].f += v[t];
                mincost += v[t] * map[i][j].w;
            }
             else
            {
                map[j][i].f -= v[t];
                mincost -= v[t] * map[j][i].w;
            }
            j = i;
        }
    }
     return  mincost;
}
int  main()
{
     int  i,j,k;
     while (scanf( " %d%d " , & r, & c) != EOF && r && c)
    {
        memset(map, 0 , sizeof (map));
        memset(man, 0 , sizeof (man));
        memset(house, 0 , sizeof (house));
        nm = nh = 0 ;
        getchar();
         for (i = 1 ;i <= r;i ++ )
        {
             for (j = 1 ;j <= c;j ++ )
            {
                scanf( " %c " , & m[i][j]);
                 if (m[i][j] == ' m ' )
                {
                    man[ ++ nm][ 0 ] = i;
                    man[nm][ 1 ] = j;
                }
                 else   if (m[i][j] == ' H ' )
                {
                    house[ ++ nh][ 0 ] = i;
                    house[nh][ 1 ] = j;
                }
            }
            getchar();
        }
        Init();
        printf( " %d\n " ,mcmf());
    }
     return   0 ;
}