有3，10，11点会TLE

这是我的代码，问问巨佬们该怎么改orzOTZ

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

int vis[1010][1010];
// int f[1010][1010];
int a[1010][1010];
int x, y;
char c;
int cnt;
int n, m;
int sum[1010][1010];
int dx[] = {0, 1, 0, -1, 0};
int dy[] = {0, 0, 1, 0, -1};

void bfs(int aa, int bb)
{
    queue<pair<int, int>> q;
    pair<int, int> t;

    q.push({aa, bb});
    vis[aa][bb] = 1;
    while (!q.empty())
    {
        t = q.front();
        q.pop();

        for (int i = 1; i <= 4; i++)
        {
            int nx = t.first + dx[i];
            int ny = t.second + dy[i];
            if (nx<1 || ny<1 || nx>n || ny>n || vis[nx][ny]==1 || a[nx][ny]==a[t.first][t.second])
            continue;
                
            vis[nx][ny] = 1;
            q.push({nx, ny});
            
        }
    }
}

int main()
{
    std::ios::sync_with_stdio(false);
    std::cin.tie(0);
    
    cin >> n >> m;
    
    
    for (int i = 1; i <= n; i++)
    {
        for (int j = 1; j <= n; j++)
        {
        	   cin >> c;
        	   a[i][j]=int(c-'0');
        	   // cout<<a[i][j];
        }
        // cout<<endl;
    }
   

    while (m--)
    {
        
        cin >> x >> y;
        
        if(sum[x][y])
        {
        	cout<<sum[x][y]<<endl;
        	continue;
        }
        memset(vis, 0, sizeof(vis));
        bfs(x, y);
        
        for (int i = 1; i <= n; i++)
        {
            for (int j = 1; j <= n; j++)
            {
                if (vis[i][j])
                {
                    cnt++;
                    // cout<<i<<' '<<j<<endl;
                }
            }
        }
        sum[x][y]=cnt;
        
        cout << cnt << endl;
        cnt = 0;
    }

    return 0;
}