HDU1565_方格取数(1)

#include <iostream>
#include <cstdio>
#include <cstring>
#define maxn 555
#define Inf 9999999
using namespace std;

int c[maxn][maxn],tag[maxn],pre[maxn],f[maxn];
int a[maxn][maxn];
int n,m,s,t,ans,tot,N=99;
int Q[maxn],bot,top;

void _init()
{
	s=0,t=n*n+1,ans=tot=0; 
	memset(c,0,sizeof c);
}

void graph()
{
	for (int i=1; i<=n; i++)
		for (int j=1; j<=n; j++)
			if ((i+j)%2==1)
			{
				int cur=i*n+j-n;
				c[s][cur]+=a[i][j];
				if (i>1) c[cur][cur-n]+=Inf;
				if (i<n) c[cur][cur+n]+=Inf;
				if (j>1) c[cur][cur-1]+=Inf;
				if (j<n) c[cur][cur+1]+=Inf;
			}
			else c[i*n+j-n][t]+=a[i][j];
}

int EK()
{
	N++;
	Q[bot=top=1]=s,f[s]=Inf,tag[s]=N;
	while (bot<=top)
	{
		int cur=Q[bot++];
		for (int i=s; i<=t; i++)
			if (c[cur][i]>0 && tag[i]!=N)
			{
				tag[i]=N;
				pre[i]=cur;
				f[i]=min(f[cur],c[cur][i]);
				Q[++top]=i;
				if (i==t)
				{
					for (int k=t; k!=s; k=pre[k])
						c[pre[k]][k]-=f[t],c[k][pre[k]]+=f[t];
					return f[t];
				}
			}
	}
	return 0;
}

int main()
{
	while (scanf("%d",&n)!=EOF)
	{
		_init();
		for (int i=1; i<=n; i++)
			for (int j=1; j<=n; j++) scanf("%d",&a[i][j]),tot+=a[i][j];
		graph();
		while (int k=EK()) ans+=k;
		printf("%d\n",tot-ans);
	}
	return 0;
}