HDU 1569 - 方格取数(2) - [最大点权独立集与最小点权覆盖集]

  1 #include<cstdio>
  2 #include<cstring>
  3 #include<vector>
  4 #include<queue>
  5 #define MAX 53*53
  6 #define INF 0x3f3f3f3f
  7 using namespace std;
  8 int m,n,map[53][53],sum; 
  9 int d[4][2]={{0,+1},{+1,0},{0,-1},{-1,0}};
 10 struct Edge{
 11     int u,v,c,f;
 12 };
 13 struct Dinic
 14 {
 15     int s,t;
 16     vector<Edge> E;
 17     vector<int> G[MAX];
 18     bool vis[MAX];
 19     int lev[MAX];
 20     int cur[MAX];
 21     void init(int l,int r) 
 22     {
 23         E.clear();
 24         for(int i=l;i<=r;i++) G[i].clear();
 25     }
 26     void addedge(int from,int to,int cap)
 27     {
 28         E.push_back((Edge){from,to,cap,0});
 29         E.push_back((Edge){to,from,0,0});
 30         G[from].push_back(E.size()-2);
 31         G[to].push_back(E.size()-1);
 32     }
 33     bool bfs()
 34     {
 35         memset(vis,0,sizeof(vis));
 36         queue<int> q;
 37         q.push(s);
 38         lev[s]=0;
 39         vis[s]=1;
 40         while(!q.empty())
 41         {
 42             int now=q.front(); q.pop();
 43             for(int i=0,_size=G[now].size();i<_size;i++)
 44             {
 45                 Edge edge=E[G[now][i]];
 46                 int nex=edge.v;
 47                 if(!vis[nex] && edge.c>edge.f)
 48                 {
 49                     lev[nex]=lev[now]+1;
 50                     q.push(nex);
 51                     vis[nex]=1;
 52                 }
 53             }
 54         }
 55         return vis[t];
 56     }
 57     int dfs(int now,int aug)
 58     {
 59         if(now==t || aug==0) return aug;
 60         int flow=0,f;
 61         for(int& i=cur[now],_size=G[now].size();i<_size;i++)
 62         {
 63             Edge& edge=E[G[now][i]];
 64             int nex=edge.v;
 65             if(lev[now]+1 == lev[nex] && (f=dfs(nex,min(aug,edge.c-edge.f)))>0)
 66             {
 67                 edge.f+=f;
 68                 E[G[now][i]^1].f-=f;
 69                 flow+=f;
 70                 aug-=f;
 71                 if(!aug) break;
 72             }
 73         }
 74         return flow;
 75     }
 76     int maxflow()
 77     {
 78         int flow=0;
 79         while(bfs())
 80         {
 81             memset(cur,0,sizeof(cur));
 82             flow+=dfs(s,INF);
 83         }
 84         return flow;
 85     }
 86 }dinic;
 87 int inmap(int i,int j)
 88 {
 89     if(1<=i && i<=m && 1<=j && j<=n) return (i-1)*n+j;
 90     else return 0;
 91 }
 92 int main()
 93 {
 94     while(scanf("%d%d",&m,&n)!=EOF)//m行n列 
 95     {
 96         dinic.init(0,m*n+1);
 97         sum=0;
 98         dinic.s=0, dinic.t=m*n+1; 
 99         for(int i=1;i<=m;i++)
100         {
101             for(int j=1;j<=n;j++)
102             {
103                 scanf("%d",&map[i][j]);
104                 sum+=map[i][j];
105                 int id=(i-1)*n+j;
106                 if((i+j)%2)
107                 {
108                     for(int k=0,_id;k<4;k++) if(_id=inmap(i+d[k][0],j+d[k][1])) dinic.addedge(id,_id,INF);
109                     dinic.addedge(dinic.s,id,map[i][j]);
110                 }
111                 else dinic.addedge(id,dinic.t,map[i][j]);
112             }
113         }
114         printf("%d\n",sum-dinic.maxflow());
115     }
116 }