Connected Cells in a Grid

• Time : O(nm)
• Space : O(nm)

int bfs(vector<vector<int>>& g, int sy, int sx) {
    int n = g.size(), m = g[0].size(), res = 1;
    int dy[8] = {-1,-1,-1,0,1,1,1,0}, dx[8] = {-1,0,1,1,1,0,-1,-1};
    queue<pair<int, int>> q;
    q.push({sy, sx});
    g[sy][sx] = 0;
    
    while(!q.empty()) {
        auto [y, x] = q.front(); q.pop();
        for(int i = 0; i < 8; i++) {
            auto ny = y + dy[i], nx = x + dx[i];
            if(0 <= ny and ny < n and 0 <= nx and nx < m and g[ny][nx]) {
                g[ny][nx] = 0;
                res++;
                q.push({ny, nx});
            }
        }
    }
    return res;
}

int connectedCell(vector<vector<int>> matrix) {
    int n = matrix.size(), m = matrix[0].size(), res = 0;
    
    for(int i = 0; i < n; i++) {
        for(int j = 0; j < m; j++) {
            if(matrix[i][j]) {
                res = max(res, bfs(matrix, i, j));
            }
        }
    }
    
    return res;
}