只AC了两个点，WA了4个点，TLE了5个点。

代码如下（求调）：

#include <bits/stdc++.h>
using namespace std;

int n,m,sum,x3,y3;
int a[5010][5010],ans[5010][5010],vis[5010][5010];
char aaaa[5010][5010];
int x1[]={0,-1,0,0,1};
int y21[]={0,0,-1,1,0};
struct d{
	int xx,yy;
}aa[1000001];

void f(int x,int y){
	for(int i=1;i<=n;i++){
		int x2=x-x1[i];
		int y2=y-y21[i];
		if(a[x][y]+a[x2][y2]==1&&!vis[x2][y2]&&x2<=n&&y2<=n&&x2>=1&&y2>=1){
			vis[x2][y2]=1;
			sum++;
			aa[sum].xx=x2;
			aa[sum].yy=y2;
//			cout<<x2<<" "<<y2<<endl;
			f(x2,y2);
		} 
	}
}

int main()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			cin>>aaaa[i][j];
			a[i][j]=aaaa[i][j]-'0';
		}
	}
	for(int i=1;i<=m;i++){
		cin>>x3>>y3;
		if(ans[x3][y3]){
			cout<<ans[x3][y3]<<endl;
		}
		else{
			sum=1;
			vis[x3][y3]=1;
			f(x3,y3);
			for(int i=1;i<=sum;i++){
				ans[aa[i].xx][aa[i].yy]=sum;
				vis[aa[i].xx][aa[i].yy]=0;
			}
			ans[x3][y3]=sum;
			cout<<sum<<endl;
		}
	}
	return 0;
}