<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 {
    int n,m;
    vector<vector<int>> g;
    int xArr[4]={0,0,1,-1};
    int yArr[4]={1,-1,0,0};
    void f(int x,int y,int z){
        if(x<0||y<0||x>=n||y>=m||g[x][y]!=z)return;
        g[x][y]=z+1;
        for(int i=0;i<4;++i){
            int newX=x+xArr[i];
            int newY=y+yArr[i];
            f(newX,newY,z);
        }
    }
public:
    int minDays(vector<vector<int>>& grid) {
        n=grid.size();
        m=grid[0].size();
        g=grid;
        int islands=0;
        for(int i=0;i<n;++i){
            for(int j=0;j<m;++j){
                if(g[i][j]==1){
                    f(i,j,1);
                    islands++;
                }
            }
        }
        if(islands!=1)return 0;
        for(int i=0;i<n;++i){
            for(int j=0;j<m;++j){
                if(g[i][j]!=0){
                    int z=g[i][j];
                    g[i][j]=0;
                    bool yes=false;
                    for(int a=0;a<n;++a){
                        for(int b=0;b<m;++b){
                            if(g[a][b]==z){
                                if(yes)return 1;
                                f(a,b,z);
                                yes=true;
                            }
                        }
                    }
                    if(!yes)return 1;
                    g[i][j]=z+1;
                }
            }
        }
        return 2;
    }
};
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