hdu 1565&&hdu 1569 (最大点权独立集)

#include<stdio.h>
#include<string.h>
const int N=2510;
const int inf=0x3fffffff;
int dis
,gap
,head
,num,start,end,ans;
struct edge
{
int ed,flow,next;
}e[N*6];
void addedge(int x,int y,int w)
{
e[num].ed=y;e[num].flow=w;e[num].next=head[x];head[x]=num++;
e[num].ed=x;e[num].flow=0;e[num].next=head[y];head[y]=num++;
}
int dfs(int u,int minflow)
{
if(u==end)return minflow;
int i,v,f,min_dis=ans-1,flow=0;
for(i=head[u];i!=-1;i=e[i].next)
{
v=e[i].ed;
if(e[i].flow<=0)continue;
if(dis[v]+1==dis[u])
{
f=dfs(v,e[i].flow>minflow-flow?minflow-flow:e[i].flow);
e[i].flow-=f;
e[i^1].flow+=f;
flow+=f;
if(flow==minflow)break;
if(dis[start]>=ans)return flow;
}
min_dis=min_dis>dis[v]?dis[v]:min_dis;
}
if(flow==0)
{
if(--gap[dis[u]]==0)
dis[start]=ans;
dis[u]=min_dis+1;
gap[dis[u]]++;
}
return flow;
}
int isap()
{
int maxflow=0;
memset(dis,0,sizeof(dis));
memset(gap,0,sizeof(gap));
gap[0]=ans;
while(dis[start]<ans)
maxflow+=dfs(start,inf);
return maxflow;
}
int main()
{
int i,n,w,j,x,sum,m;
while(scanf("%d%d",&n,&m)!=-1)
{
memset(head,-1,sizeof(head));
num=0;sum=0;start=0;end=n*m+1;ans=end+1;
for(i=1;i<=n;i++)
{
for(j=1;j<=m;j++)
{
x=i*m+j-m;
scanf("%d",&w);
sum+=w;
if((i+j)%2!=0)
addedge(x,end,w);
else
{
addedge(start,x,w);
if(i>1)addedge(x,x-m,inf);
if(j>1)addedge(x,x-1,inf);
if(i<n)addedge(x,x+m,inf);
if(j<m)addedge(x,x+1,inf);
}
}
}
printf("%d\n",sum-isap());
}
return 0;
}