<p>You are given an <code>m x n</code> binary grid <code>grid</code> where <code>1</code> represents land and <code>0</code> represents water. An <strong>island</strong> is a maximal <strong>4-directionally</strong> (horizontal or vertical) connected group of <code>1</code>&#39;s.</p>

<p>The grid is said to be <strong>connected</strong> if we have <strong>exactly one island</strong>, otherwise is said <strong>disconnected</strong>.</p>

<p>In one day, we are allowed to change <strong>any </strong>single land cell <code>(1)</code> into a water cell <code>(0)</code>.</p>

<p>Return <em>the minimum number of days to disconnect the grid</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/12/24/land1.jpg" style="width: 500px; height: 169px;" />
<pre>
<strong>Input:</strong> grid = [[0,1,1,0],[0,1,1,0],[0,0,0,0]]

<strong>Output:</strong> 2
<strong>Explanation:</strong> We need at least 2 days to get a disconnected grid.
Change land grid[1][1] and grid[0][2] to water and get 2 disconnected island.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/12/24/land2.jpg" style="width: 404px; height: 85px;" />
<pre>
<strong>Input:</strong> grid = [[1,1]]
<strong>Output:</strong> 2
<strong>Explanation:</strong> Grid of full water is also disconnected ([[1,1]] -&gt; [[0,0]]), 0 islands.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 30</code></li>
	<li><code>grid[i][j]</code> is either <code>0</code> or <code>1</code>.</li>
</ul>

class Solution {
public:
    void bfs(int i, int j, int n, int m, vector<vector<int>>& grid, vector<vector<bool>>& vis)
    {
        queue<pair<int,int>> q;
        q.push({i, j});
        vis[i][j] = true;

        while(!q.empty())
        {
            int row = q.front().first;
            int col = q.front().second;
            q.pop();

            for(int delrow = -1; delrow <= 1; delrow++)
            {
                for(int delcol = -1; delcol <= 1; delcol++)
                {
                    int nrow = delrow + row;
                    int ncol = delcol + col;

                    if(nrow >= 0 && nrow < n && ncol >= 0 && ncol < m && abs(delrow) != abs(delcol) && grid[nrow][ncol] == 1 && !vis[nrow][ncol])
                    {
                        q.push({nrow, ncol});
                        vis[nrow][ncol] = true;
                    }
                }
            }
        }
    }

    int bfs1(vector<vector<int>>& grid)
    {
        int n = grid.size();
        int m = grid[0].size();
        vector<vector<bool>> vis(n, vector<bool>(m, false));
        int cnt = 0;

        for(int i = 0; i < n; i++)
        {
            for(int j = 0; j < m; j++)
            {
                if(grid[i][j] == 1 && !vis[i][j])
                {
                    cnt++;
                    queue<pair<int,int>> q;
                    q.push({i, j});
                    vis[i][j] = true;

                    while(!q.empty())
                    {
                        int row = q.front().first;
                        int col = q.front().second;
                        q.pop();

                        for(int delrow = -1; delrow <= 1; delrow++)
                        {
                            for(int delcol = -1; delcol <= 1; delcol++)
                            {
                                int nrow = delrow + row;
                                int ncol = delcol + col;

                                if(nrow >= 0 && nrow < n && ncol >= 0 && ncol < m && abs(delrow) != abs(delcol) && grid[nrow][ncol] == 1 && !vis[nrow][ncol])
                                {
                                    q.push({nrow, ncol});
                                    vis[nrow][ncol] = true;
                                }
                            }
                        }
                    }
                }
            }
        }
        return cnt;
    }

    int minDays(vector<vector<int>>& grid) {
        if(bfs1(grid) == 0)
        {
            return 0;
        }
        int n = grid.size(); 
        int m = grid[0].size();
 
        int cnt_island = 0;
        vector<vector<bool>> vis(n, vector<bool>(m, false));

        for(int i = 0; i < n; i++)
        {
            for(int j = 0; j < m; j++)
            {
                if(grid[i][j] == 1 && !vis[i][j])
                {
                    cnt_island++;
                    bfs(i, j, n, m, grid, vis);
                }
            }
        }

        if(cnt_island > 1)
        {
            return 0;
        }

        for(int i = 0; i < n; i++)
        {
            for(int j = 0; j < m; j++)
            {
                if(grid[i][j] == 1)
                {
                    grid[i][j] = 0;
                    int res = bfs1(grid);
                    if(res != 1)
                    {
                        return 1;
                    }
                    grid[i][j] = 1;
                }
            }
        }

        return 2;
    }
};
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