应该是无限递归了，全是MLE

#include<cstdio>
#include<cstring>
#include<algorithm>
using namespace std;
int t,n,m,mp[7][7],ans[21],k=1,mx[4]={1,0,-1,0},my[4]={0,1,0,-1};
bool vis[7][7];
void f1(int x,int y)
{
	vis[x][y]=true;
	vis[x][y+1]=true;
	vis[x][y-1]=true;
	vis[x+1][y]=true;
	vis[x+1][y+1]=true;
	vis[x+1][y-1]=true;
	vis[x-1][y]=true;
	vis[x-1][y+1]=true;
	vis[x-1][y-1]=true;
	return;
}
void f2(int x,int y)
{
	vis[x][y]=false;
	vis[x][y+1]=false;
	vis[x][y-1]=false;
	vis[x+1][y]=false;
	vis[x+1][y+1]=false;
	vis[x+1][y-1]=false;
	vis[x-1][y]=false;
	vis[x-1][y+1]=false;
	vis[x-1][y-1]=false;
	return;
}
void dfs(int x,int y,int sum)
{
	if(x==n&&y==m)
	{
		ans[k]=max(ans[k],sum);
		return;
	}
	for(int i=0;i<4;i++)
	{
		if(x+mx[i]>n||y+my[i]>m||vis[x+mx[i]][y+my[i]]) continue;
		x+=mx[i];y+=my[i];
		vis[x][y]=true;
		dfs(x,y,sum);
		vis[x][y]=false;
		f1(x,y);
		sum+=mp[x][y];
		dfs(x,y,sum);
		sum-=mp[x][y];
		f2(x,y);
		x-=mx[i];y-=my[i];
	}
}
int main()
{
	scanf("%d",&t);
	while(t--)
	{
		memset(mp,0,sizeof(mp));
		memset(vis,false,sizeof(vis));
		ans[k]=-1;
		scanf("%d%d",&n,&m);
		for(int i=1;i<=n;i++) for(int j=1;j<=m;j++) scanf("%d",&mp[i][j]);
		dfs(1,1,0); 
		k++;
    }
	for(int i=1;i<=k;i++) printf("%d\n",ans[i]);
 	return 0;
}