<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 {
    const vector<int> dx={1,-1,0,0};
    const vector<int> dy={0,0,1,-1};
    bool is1(vector<vector<int>>& grid, int i, int j)
    {
        if(i<0||i>=grid.size()||j<0||j>=grid[0].size())
            return false;
        else if(grid[i][j]!=1)
            return false;
        return true;
    }
    bool connected(vector<vector<int>> grid){
        int width=grid[0].size();
        int height=grid.size();
        int i,j;
        for(i=0;i<height;i++)
            for(j=0;j<width;j++)
            {
                if(grid[i][j]==1)
                    goto START;
            }
        if(i==height&&j==width)
            return false;
        START:
        vector<int> x(1,i);
        vector<int> y(1,j);
        int tempx;
        int tempy;
        while(!x.empty())
        {
            tempx=x.back();
            tempy=y.back();
            grid[tempx][tempy]=0;
            x.pop_back();
            y.pop_back();
            for(i=0;i<4;i++)
                if(is1(grid,tempx+dx[i],tempy+dy[i]))
                {
                    x.push_back(tempx+dx[i]);
                    y.push_back(tempy+dy[i]);
                }
        }
        for(i=0;i<grid.size();i++)
            for(j=0;j<grid[0].size();j++)
                if(grid[i][j]==1)
                    return false;
        return true;
    }
public:
    int minDays(vector<vector<int>>& grid) {
        if(!connected(grid))
            return 0;
        int i,j;
        for(i=0;i<grid.size();i++)
            for(j=0;j<grid[0].size();j++)
            {
                if(grid[i][j]==1)
                {
                    grid[i][j]=0;
                    if(!connected(grid))
                        return 1;
                    grid[i][j]=1;
                }
            }
        return 2;
    }
};
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