hdu1565二分图点权最大独立集

分析：同上一道题是一样的，就是一个方格取数的模型。

#include <iostream>
#include <cstdio>
using namespace std;
const int oo=1e9;
const int mm=111111;
const int mn=999;
struct Node
{
int i,j,id,c;
}nod[mm*mn];

int node,src,dest,edge;
int ver[mm],flow[mm],next[mm];
int head[mn],work[mn],dis[mn],q[mn];
void prepare(int _node,int _src,int _dest)
{
node=_node,src=_src,dest=_dest;
for(int i=0;i<node;i++) head[i]=-1;
edge=0;
}
void addedge(int u,int v,int c)
{
ver[edge]=v;flow[edge]=c;next[edge]=head[u];head[u]=edge++;
ver[edge]=u;flow[edge]=0;next[edge]=head[v];head[v]=edge++;
}
bool Dinic_bfs()
{
int i,u,v,l,r=0;
for(i=0;i<node;i++)
dis[i]=-1;
dis[q[r++]=src]=0;
for(l=0;l<r;l++)
for(i=head[u=q[l]];i>=0;i=next[i])
if(flow[i]&&dis[v=ver[i]]<0)
{
dis[q[r++]=v]=dis[u]+1;
if(v==dest) return 1;
}
return 0;
}
int Dinic_dfs(int u,int exp)
{
if(u==dest) return exp;
for(int &i=work[u],v,tmp;i>=0;i=next[i])
{
if(flow[i]&&dis[v=ver[i]]==dis[u]+1&&(tmp=Dinic_dfs(v,min(exp,flow[i])))>0)
{
flow[i]-=tmp;
flow[i^1]+=tmp;
return tmp;
}
}
return 0;
}
int Dinic_flow()
{
int i,ret=0,delta;
while(Dinic_bfs())
{
for(i=0;i<node;i++)
work[i]=head[i];
while(delta=Dinic_dfs(src,oo)) ret+=delta;

}
return ret;
}
int main()
{
int n,u,v,a,k,tmpx,tmpy,sum;
while(~scanf("%d",&n))
{
prepare(n*n+2,0,n*n+1);
u=0;v=n*n-n*n/2;k=-1;sum=0;
for(int i=0;i<n;i++)
{
for(int j=0;j<n;j++)
{
scanf("%d",&nod[++k].c);
sum+=nod[k].c;
nod[k].i=i;nod[k].j=j;
if((i+j)%2==0)
{
u++;
nod[k].id=u;
}
else
{
v++;
nod[k].id=v;
}
}
}
for(int i=0;i<=k;i++)
{
//cout<<"i="<<nod[i].i<<" j="<<nod[i].j<<" c="<<nod[i].c<<" id="<<nod[i].id<<endl;
if(nod[i].id<=n*n-n*n/2)
addedge(0,nod[i].id,nod[i].c);
else
addedge(nod[i].id,n*n+1,nod[i].c);
}
for(int i=0;i<=k;i++)
if(nod[i].id<=n*n-n*n/2)
{
tmpx=nod[i].i;
tmpy=nod[i].j;
if(tmpx-1>=0) addedge(nod[i].id,nod[i-n].id,oo);
if(tmpx+1<n) addedge(nod[i].id,nod[i+n].id,oo);
if(tmpy-1>=0) addedge(nod[i].id,nod[i-1].id,oo);
if(tmpy+1<n) addedge(nod[i].id,nod[i+1].id,oo);
}
printf("%d\n",sum-Dinic_flow());
}
return 0;
}