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  • hdu4971 流-最大权闭包

    题意:
          给了一些任务,然后给了一些完成某些任务的限制,然后又给了限制之间的拓扑关系,最后问你最大收益。

    思路:
          很直白,就是流的一个应用,最大权闭包,没涉及到什么想法的地方,建图也不坑,直接说建图吧,
    s - 所有任务  流量是 任务价值
    所有限制 - t  流量是 限制代价
    a -> b 流量 INF a限制的拓扑关系在b的后面

    最后答案是 所有任务的价值 - maxflow


    #include<stdio.h>
    #include<string.h>
    #include<queue>
    
    #define N_node 100
    #define N_edge 8000
    #define INF 1000000000
    
    using namespace std;
    
    typedef struct
    {
       int to ,next ,cost;
    }STAR;
    
    typedef struct
    {
       int x ,t;
    }DEP;
    
    STAR E[N_edge];
    DEP xin ,tou;
    int list[N_node] ,listt[N_node] ,tot;
    int deep[N_node];
    
    void add(int a ,int b ,int c)
    {
       E[++tot].to = b;
       E[tot].cost = c;
       E[tot].next = list[a];
       list[a] = tot;
       
       E[++tot].to = a;
       E[tot].cost = 0;
       E[tot].next = list[b];
       list[b] = tot;
    }
    
    bool BFS_Deep(int s ,int t ,int n)
    {
       memset(deep ,255 ,sizeof(deep));
       deep[s] = 0;
       xin.x = s ,xin.t = 0;
       queue<DEP>q;
       q.push(xin);
       while(!q.empty())
       {
          tou = q.front();
          q.pop();
          for(int k = list[tou.x] ;k ;k = E[k].next)
          {
             xin.x = E[k].to;
             xin.t = tou.t + 1;
             if(deep[xin.x] != -1 || !E[k].cost)
             continue;
             deep[xin.x] = xin.t;
             q.push(xin);
          }
        }
        for(int i = 0 ;i <= n ;i ++)
        listt[i] = list[i];
        return deep[t] != -1;
    }
    
    int minn(int x ,int y)
    {
        return x < y ? x : y;
    }
    
    int DFS_Flow(int s ,int t ,int flow)
    {
        if(s == t) return flow;
        int nowflow = 0;
        for(int k = listt[s] ;k ;k = E[k].next)
        {
           listt[s] = k;
           int to = E[k].to;
           int c = E[k].cost;
           if(deep[to] != deep[s] + 1 || !c)
           continue;
           int tmp = DFS_Flow(to ,t ,minn(c ,flow - nowflow));
           nowflow += tmp;
           E[k].cost -= tmp;
           E[k^1].cost += tmp;
           if(nowflow == flow) break;
         }
         if(!nowflow) deep[s] = 0;
         return nowflow;
    }
    
    int DINIC(int s ,int t ,int n)
    {
        int ans = 0;
        while(BFS_Deep(s ,t ,n))
        {
           ans += DFS_Flow(s ,t ,INF);
        }
        return ans;
    }
    
    int main ()
    {
        int i ,j ,n ,nn ,m ,a ,T ,cas = 1;
        int s ,t ,sum_z;
        scanf("%d" ,&T);
        while(T--)
        {
           scanf("%d %d" ,&n ,&m);
           s = 0 ,t = n + m + 1;
           memset(list ,0 ,sizeof(list)) ,tot = 1;
           for(sum_z = 0 ,i = 1 ;i <= n ;i ++)
           {
              scanf("%d" ,&a);
              sum_z += a;
              add(s ,i ,a);
           }
           for(i = 1 ;i <= m ;i ++)
           {
              scanf("%d" ,&a);
              add(i + n ,t ,a);
           }
           for(i = 1 ;i <= n ;i ++)
           {
              scanf("%d" ,&nn);
              while(nn--)
              {
                  scanf("%d" ,&a);
                  a ++;
                  add(i ,a + n ,INF);
              }
           }
           for(i = 1 ;i <= m ;i ++)
           for(j = 1 ;j <= m ;j ++)
           {
              scanf("%d" ,&a);
              if(a) add(i + n ,j + n ,INF);
           }
           printf("Case #%d: " ,cas ++);
           printf("%d
    " ,sum_z - DINIC(s ,t ,t));
        }
        return 0;
    }
              
    
           
    


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  • 原文地址:https://www.cnblogs.com/csnd/p/12062841.html
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