counting cells in a blob

#include<bits/stdc++.h>
#define pii pair<int, int>
using namespace std;
int fx[]= {+0,+0,+1,-1,-1,+1,-1,+1};
int fy[]= {-1,+1,+0,+0,+1,+1,-1,-1};
int  ans;
string grid[26];
bool vis[26][26];
void bfs(int sx, int sy, int n, int m)
{
    int cnt = 1;
    vis[sx][sy] = true;
    queue<pii>q;
    q.push(pii(sx, sy));
    while(!q.empty())
    {
        pii top = q.front();
        q.pop();
        for(int i = 0; i < 8; i++)
        {
            int tx = top.first + fx[i];
            int ty = top.second + fy[i];
            if(tx >= 0 && tx < n && ty >= 0 && ty < m && vis[tx][ty] == false && grid[tx][ty] == '1')
            {
                vis[tx][ty] = true;
                grid[tx][ty] = '0';
                q.push(pii(tx, ty));
                cnt++;
            }
        }
    }
    // cout << "cnt = " << cnt << endl;
    ans = max(ans, cnt);
}
int main()
{
    int tc;
    while(cin >> tc)
    {
        while(tc--)
        {
            int row = 0, col;
            while(cin >> grid[row])
            {
                col = grid[row].size();
                if(col == 0 )
                    break;
                row++;
            }
            for(int i = 0; i < row; i++)
            {
                for(int j = 0; j < col; j++)
                {
                    if(grid[i][j] == '1')
                        bfs(i, j, row, col);
                }
            }
            //cout << "len = " << len << endl;
            cout << ans << endl;
            if(tc)
                cout << endl;
            memset(vis, 0, sizeof(vis));
            for(int i = 0; i < row; i++)
                grid[i].clear();
            ans = 0;
        }
    }
    return 0;
}