<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 fill(vector<vector<int>>& grid, int i, int j, int rows, int cols) {
        queue<pair<int,int>> q;
        q.push({i, j});
        while(!q.empty()) {
            int a = q.front().first;
            int b = q.front().second; 
            q.pop();
            if (a + 1 < rows && grid[a + 1][b]) {
                grid[a + 1][b] = 0;
                q.push({a + 1, b});
            }
            if (a - 1 >= 0 && grid[a - 1][b]) {
                grid[a - 1][b] = 0;
                q.push({a - 1, b});
            }
            if (b + 1 < cols && grid[a][b + 1]) {
                grid[a][b + 1] = 0;
                q.push({a, b + 1});
            }
            if (b - 1 >= 0 && grid[a][b - 1]) {
                grid[a][b - 1] = 0;
                q.push({a, b - 1});
            }
        }
    } 

    int minDays(vector<vector<int>>& grid) {
        int rows = grid.size();
        int cols = grid[0].size();
        int num_islands = 0;
        vector<vector<int>> grid_copy = grid;
        for (int i = 0; i < rows; i++) {
            for (int j = 0; j < cols; j++) {
                if (grid_copy[i][j]) {
                    grid_copy[i][j] = 0;
                    fill(grid_copy, i, j, rows, cols);
                    num_islands++;
                }
            }
        }
        if (num_islands != 1) {
            return 0;
        }
        for (int k = 0; k < rows; k++) {
            for (int l = 0; l < cols; l++) {
                num_islands = 0;
                vector<vector<int>> grid_copy = grid;
                grid_copy[k][l] = 0;
                for (int i = 0; i < rows; i++) {
                    for (int j = 0; j < cols; j++) {
                        if (grid_copy[i][j]) {
                            fill(grid_copy, i, j, rows, cols);
                            num_islands++;
                        }
                    }
                }
                if (num_islands != 1) {
                    return 1;
                }
            }
        }
        return 2;
    }
};
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