<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:
int n,m;
    void DFS(vector<vector<bool>>& visited,int i,int j,vector<vector<int>>& grid)
    {
        if(i>=m || i<0 || j>=n || j<0 || grid[i][j]==0 || visited[i][j])
        {
            return;
        }
        visited[i][j]=true;

        DFS(visited,i+1,j,grid);
        DFS(visited,i,j+1,grid);
        DFS(visited,i-1,j,grid);
        DFS(visited,i,j-1,grid);
    }
    int no_of_islands(vector<vector<int>>& grid)
    {
        vector<vector<bool>> visited(m,vector<bool>(n));

        int islands=0;

        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                if(grid[i][j]==1 && !visited[i][j])
                {
                    DFS(visited,i,j,grid);
                    islands++;   
                }
            }
        }
        return islands;
    } 
    int minDays(vector<vector<int>>& grid) {

        m=grid.size();
        n=grid[0].size();

        int islands=no_of_islands(grid);

        if(islands==0 || islands>1)
        {
            return 0;
        }
        else
        {
            for(int i=0;i<m;i++)
            {
                for(int j=0;j<n;j++)
                {
                    if(grid[i][j]==1)
                    {
                        grid[i][j]=0;

                        if(no_of_islands(grid)>1 || no_of_islands(grid)==0)
                        {
                            return 1;
                        }

                        grid[i][j]=1;
                    }
                }
            }
        }
        return 2;
    }
};
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