<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:
    bool singleIsland(vector<vector<int>> grid){
        int i, j;
        for(i = 0; i < grid.size(); i++){
            for(j = 0; j < grid[0].size(); j++)
                if(grid[i][j] == 1) break;
            if(j != grid[0].size()) break;
        }
        if(i >= grid.size() || j >= grid[0].size()) return false;
        //Flood the island
        stack<pair<int,int>> q;
        q.push(make_pair(i,j));
        while(!q.empty()){
            pair<int,int> land = q.top();
            q.pop();
            grid[land.first][land.second] = 0;
            if(land.first+1 < grid.size() && grid[land.first+1][land.second] == 1) q.push(make_pair(land.first+1, land.second));
            if(land.second+1 < grid[0].size() && grid[land.first][land.second+1] == 1) q.push(make_pair(land.first, land.second+1));
            if(land.first-1 >= 0 && grid[land.first-1][land.second] == 1) q.push(make_pair(land.first-1, land.second));
            if(land.second-1 >= 0 && grid[land.first][land.second-1] == 1) q.push(make_pair(land.first, land.second-1));
        }
        for(; i < grid.size(); i++){
            for(j=0; j < grid[0].size(); j++){
                if(grid[i][j] == 1)
                    return false;
            }
        }
        return true;
    }

    int minDays(vector<vector<int>>& grid) {
        
        if(singleIsland(grid)){
            for(int i = 0; i < grid.size(); i++){
                for(int j = 0 ; j < grid[0].size(); j++){
                    if(grid[i][j] == 1){
                        int count = 0;
                        if(i+1 < grid.size() && grid[i+1][j] == 1) count++;
                        if(j+1 < grid[0].size() && grid[i][j+1] == 1) count++;
                        if(i-1 >= 0 && grid[i-1][j] == 1) count++;
                        if(j-1 >= 0 && grid[i][j-1] == 1) count++;
                        grid[i][j] = 0;
                        if(!singleIsland(grid)) return 1;
                        grid[i][j] = 1;
                    }
                }
            }
            return 2;
        }
        return 0;
    }
};
51340