TYVJ1338 QQ农场

  1 /*by SilverN*/
  2 #include<iostream>
  3 #include<algorithm>
  4 #include<cstring>
  5 #include<cstdio>
  6 #include<cmath>
  7 #include<queue>
  8 using namespace std;
  9 const int INF=1e9;
 10 const int mxn=50100;
 11 const int mx[5]={0,1,0,-1,0};
 12 const int my[5]={0,0,1,0,-1};
 13 int read(){
 14     int x=0,f=1;char ch=getchar();
 15     while(ch<‘0‘ || ch>‘9‘){if(ch==‘-‘)f=-1;ch=getchar();}
 16     while(ch>=‘0‘ && ch<=‘9‘){x=x*10+ch-‘0‘;ch=getchar();}
 17     return x*f;
 18 }
 19 struct edge{
 20     int v,nxt,f;
 21 }e[mxn*20];
 22 int hd[mxn],mct=1;
 23 void add_edge(int u,int v,int c){
 24     e[++mct].v=v;e[mct].f=c;e[mct].nxt=hd[u];hd[u]=mct;return;
 25 }
 26 void insert(int u,int v,int c){
 27     add_edge(u,v,c);add_edge(v,u,0);return;
 28 }
 29 int n,m,S,T;
 30 int d[mxn];
 31 bool BFS(){
 32     memset(d,0,sizeof d);
 33     d[S]=1;
 34     queue<int>q;
 35     q.push(S);
 36     while(!q.empty()){
 37         int u=q.front();q.pop();
 38         for(int i=hd[u];i;i=e[i].nxt){
 39             int v=e[i].v;
 40             if(!d[v] && e[i].f){
 41                 d[v]=d[u]+1;q.push(v);
 42             }
 43         }
 44     }
 45     return d[T];
 46 }
 47 int DFS(int u,int lim){
 48     if(u==T)return lim;
 49     int tmp,f=0;
 50     for(int i=hd[u];i;i=e[i].nxt){
 51         int v=e[i].v;
 52         if(d[v]==d[u]+1 && e[i].f){
 53             tmp=DFS(v,min(lim,e[i].f));
 54             e[i].f-=tmp;
 55             e[i^1].f+=tmp;
 56             lim-=tmp;
 57             f+=tmp;
 58             if(!lim)return f;
 59         }
 60     }
 61     d[u]=0;
 62     return f;
 63 }
 64 int Dinic(){
 65     int res=0;
 66     while(BFS())res+=DFS(S,INF);
 67     return res;
 68 }
 69 int mp[210][210];
 70 int id[210][210],cnt=0;
 71 int main(){
 72     int i,j;
 73     n=read();
 74     S=0;T=n*n+1;
 75     for(i=1;i<=n;i++)
 76         for(j=1;j<=n;j++)
 77             id[i][j]=++cnt;
 78     int smm=0;int nx,ny;
 79     for(i=1;i<=n;i++)
 80         for(j=1;j<=n;j++){
 81             mp[i][j]=read();
 82             smm+=mp[i][j];
 83             if(((i+j)&1)==0){
 84                 insert(S,id[i][j],mp[i][j]);
 85                 for(int k=1;k<=4;k++){
 86                     nx=i+mx[k];
 87                     ny=j+my[k];
 88                     if(nx || nx<=n || ny || ny<=n){
 89                         insert(id[i][j],id[nx][ny],INF);
 90                     }
 91                 }
 92             }
 93             else{
 94                 insert(id[i][j],T,mp[i][j]);
 95             }
 96         }
 97     int ans=smm-Dinic();
 98     printf("%d\n",ans);
 99     return 0;
100 }