Minimum Number of Days to Disconnect Island
<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://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/1500-1599/1568.Minimum%20Number%20of%20Days%20to%20Disconnect%20Island/images/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://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/1500-1599/1568.Minimum%20Number%20of%20Days%20to%20Disconnect%20Island/images/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>
Depth-First Search; Breadth-First Search; Array; Matrix; Strongly Connected Component
/**
 * @param {number[][]} grid
 * @return {number}
 */
var minDays = function (grid) {
    const dirs = [-1, 0, 1, 0, -1];
    const [m, n] = [grid.length, grid[0].length];

    const dfs = (i, j, visited) => {
        if (i < 0 || m <= i || j < 0 || n <= j || grid[i][j] === 0 || visited[i][j]) {
            return;
        }

        visited[i][j] = true;
        for (let d = 0; d < 4; d++) {
            const [y, x] = [i + dirs[d], j + dirs[d + 1]];
            dfs(y, x, visited);
        }
    };

    const count = () => {
        const vis = Array.from({ length: m }, () => Array(n).fill(false));
        let c = 0;
        for (let i = 0; i < m; i++) {
            for (let j = 0; j < n; j++) {
                if (grid[i][j] === 1 && !vis[i][j]) {
                    c++;
                    dfs(i, j, vis);
                }
            }
        }
        return c;
    };

    if (count() !== 1) return 0;

    for (let i = 0; i < m; i++) {
        for (let j = 0; j < n; j++) {
            if (grid[i][j] === 1) {
                grid[i][j] = 0;
                if (count() !== 1) return 1;
                grid[i][j] = 1;
            }
        }
    }

    return 2;
};
