<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 dfs(vector<vector<int>> &temp, int m, int n, int i, int j){
        if (i<0 || j<0 || i>=m || j>=n || temp[i][j]==0) return;
        temp[i][j] = 0;
        dfs(temp, m, n, i+1, j);
        dfs(temp, m, n, i, j+1);
        dfs(temp, m, n, i-1, j);
        dfs(temp, m, n, i, j-1);
    }
    int help(vector<vector<int>> temp, int m, int n){
        int ans = 0;
        for (int i = 0; i<m; ++i){
            for (int j = 0; j<n; ++j){
                if (temp[i][j]!=1) continue;
                dfs(temp, m,n , i, j);
                ans++;
            }
        }
        return ans;
    }
    int minDays(vector<vector<int>>& grid) {
        int ans = 2;
       int m = grid.size(), n = grid[0].size();
        if (help(grid, m,n)!=1) return 0;
        int no1 = 0;
        for (int i = 0; i<m; ++i){
            for (int j = 0; j<n; ++j){
                if (grid[i][j]==1) no1++;
            }
        }
        if (no1<=2) return no1;
        for (int i = 0; i<m; ++i){
            for (int j = 0; j<n; ++j){
                if (grid[i][j]==0) continue;
                int x = 0;
                if (i-1>=0 && grid[i-1][j]==1) x++;
                if (j-1>=0 && grid[i][j-1]==1) x++;
                if (i+1<m && grid[i+1][j]==1) x++;
                if (j+1<n && grid[i][j+1]==1) x++;
                ans = min(ans, x);            }
        }
        if (ans==2){
            for (int i = 0; i<m; ++i){
                for (int j = 0; j<n; ++j){
                    if (grid[i][j]==0) continue;
                    grid[i][j] = 0;
                    int t = help(grid, m, n);
                    if (t!=1) return 1;
                    grid[i][j] = 1;
            }}
        }
    return ans;
    }
};
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