为啥就过了一个hack数据

#include<bits/stdc++.h>
using namespace std;
const int N=1e3+7;
int n,m;
int ans[N][N],tot,cnt[N];
string a[N];
bool s[N][N],vis[N][N];
const int dx[4]={0,0,-1,1};
const int dy[4]={-1,1,0,0};
queue<pair<int,int>>q;
int x,y;
void bfs(){
	q.push({x,y});
	vis[x][y]=tot;
	cnt[tot]=1;
	while(q.size()){
		int x1=q.front().first,y1=q.front().second;
		//cout<<x1<<" "<<y1<<"\n";
		q.pop();
		for(int d=0;d<4;d++){
			int xx=x1+dx[d],yy=y1+dy[d];
			if((s[xx][yy]!=s[x1][y1])&&(!vis[xx][yy])&&(xx<=n&&xx>=1&&yy>=1&&yy<=n)){
				vis[xx][yy]=tot;
				cnt[tot]++;
				q.push({xx,yy});
			}
		}
	}
}
int main(){
	cin>>n>>m;
	for(int i=1;i<=n;i++){
		cin>>a[i];
		for(int j=0;a[i][j];j++){
			s[i][j+1]=a[i][j]-'0';
		}
	}
	
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++){
			if(vis[i][j]==0){
				//cout<<vis[i][j]<<"\n";
				tot++;
				//cout<<tot<<"\n";
				x=i,y=j;
				bfs();
			}
			//cout<<cnt[tot]<<"\n";
		}
	}
	for(int i=1;i<=n;i++){
		for(int j=1;j<=n;j++)cout<<vis[i][j]<<" ";
		cout<<"\n";
	}
	while(m--){
		int x,y;
		cin>>x>>y;
		cout<<cnt[vis[x][y]]<<"\n";
	}
}