【网络流24题----09】方格取数问题

  1 #include<iostream>
  2 #include<cstdio>
  3 #include<algorithm>
  4 #include<vector>
  5 #include<cstdlib>
  6 #include<cmath>
  7 #include<cstring>
  8 using namespace std;
  9 #define maxn 910
 10 #define inf 0x7fffffff
 11 #define llg int 
 12 #define yyj(a) freopen(a".in","r",stdin),freopen(a".out","w",stdout);
 13 llg n,m,e[maxn],N,p[10][5],g[50][50],k,tot,se[50][50];
 14 
 15 struct DINIC
 16 {
 17     vector<llg>a[maxn],ba[maxn],val[maxn];
 18     llg dl[maxn],deep[maxn],bj[maxn];
 19 
 20     void insert(llg x,llg y,llg z)
 21     {
 22         a[x].push_back(y),val[x].push_back(z);
 23         a[y].push_back(x),val[y].push_back(0);
 24         ba[x].push_back(a[y].size()-1); ba[y].push_back(a[x].size()-1);
 25     }
 26 
 27     llg dfs(llg x,llg low)
 28     {
 29         llg va=0,inc=0;
 30         if (x==N) return low;
 31         llg w=a[x].size();
 32         for (llg i=0;i<w;i++)
 33             if (deep[x]+1==deep[a[x][i]] && val[x][i]>0 && (va=dfs(a[x][i],min(low,val[x][i]))))
 34             {
 35                 val[x][i]-=va; val[a[x][i]][ba[x][i]]+=va; inc+=va;
 36                 return va;
 37             }
 38         if (!inc) deep[x]=-1;
 39         return 0;
 40     }
 41 
 42     void fencen()
 43     {
 44         llg x,w,v; deep[0]=0;
 45         memset(bj,0,sizeof(bj));
 46         llg head=0,tail=1; dl[1]=0; bj[0]=1;
 47         do
 48         {
 49             x=dl[++head]; w=a[x].size();
 50             for (llg i=0;i<w;i++)
 51             {
 52                 v=a[x][i];
 53                 if (bj[v] || val[x][i]<=0) continue;
 54                 dl[++tail]=v;
 55                 deep[v]=deep[x]+1; bj[v]=1;
 56             }
 57         }while (head!=tail);
 58     }
 59 
 60     llg dinic()
 61     {
 62         llg ans=0;
 63         while (1)
 64         {
 65             fencen();
 66             if (!bj[N]) break;
 67             ans+=dfs(0,inf);
 68         }
 69         return ans;
 70     }
 71 
 72     void oupt()
 73     {
 74         for (llg i=1;i<=k;i++)
 75         {
 76             printf("%d: ",i);
 77             llg w=a[i].size();
 78             for (llg e=0;e<w;e++)
 79             {
 80                 llg v=a[i][e];
 81                 if (v>k && v<N && val[i][e]==0) printf("%d ",v-k); 
 82             }
 83             printf("\n");
 84         }
 85     }
 86 }G;
 87 
 88 llg ma(llg x,llg y) {return x*m-m+y;}
 89 
 90 void init()
 91 {
 92     p[1][1]=1,p[2][1]=-1,p[3][2]=1,p[4][2]=-1;
 93     cin>>n>>m;
 94     N=n*m+1;
 95     for (llg i=1;i<=n;i++)
 96         for (llg j=1;j<=m;j++)
 97             scanf("%d",&g[i][j]),tot+=g[i][j];
 98     for (llg i=1;i<=n;i++)
 99         for (llg j=1;j<=m;j++)
100         {
101             for (llg k=1;k<=4;k++)
102                 {
103                     llg x=i+p[k][1],y=j+p[k][2];
104                     if (x>n || x<1 || y>m || y<1) continue;
105                     se[x][y]=(se[i][j]+1)%2;
106                 }
107         }
108     for (llg i=1;i<=n;i++)
109         for (llg j=1;j<=m;j++)
110             if (se[i][j])
111             {
112                 for (llg k=1;k<=4;k++)
113                 {
114                     llg x=i+p[k][1],y=j+p[k][2];
115                     if (x>n || x<1 || y>m || y<1) continue;
116                     G.insert(ma(i,j),ma(x,y),inf);
117                 }
118                 G.insert(0,ma(i,j),g[i][j]);
119             }
120     for (llg i=1;i<=n;i++)
121         for (llg j=1;j<=m;j++)
122             if (!se[i][j])
123                 G.insert(ma(i,j),N,g[i][j]);
124 }
125 
126 int main()
127 {
128     yyj("grid");
129     init();
130     cout<<tot-G.dinic();
131     return 0;
132 }