<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:
    int bfs(int r, int c, vector<vector<int>>& grid, vector<vector<int>>& vis){
        int n=grid.size();
        int m=grid[0].size();
        int maxx = 1;
        int count=1;
        queue<pair<pair<int, int>, int>> q;
        vis[r][c] = 1;
        q.push({{r, c}, 1});
        int drow[4] = {-1, 0, 1, 0};
        int dcol[4] = {0, 1, 0, -1};
        while(!q.empty()){
            auto it = q.front();
            q.pop();
            int row = it.first.first;
            int col = it.first.second;
            int size = it.second;
            maxx = max(maxx, size);
            for(int i=0; i<4; i++){
                int adjr = row+drow[i];
                int adjc = col+dcol[i];
                if(adjr>=0 && adjr<n && adjc>=0 && adjc<m && vis[adjr][adjc]==0 && grid[adjr][adjc]==1){
                    vis[adjr][adjc]=1;
                    q.push({{adjr, adjc}, size+1});
                    count++;
                }
            }
        }

        return count;
    }

    int countIslands(vector<vector<int>>& grid){
        int n=grid.size();
        int m=grid[0].size();
        int count=0;
        vector<vector<int>> vis(n, vector<int>(m, 0));
        for(int i=0; i<n; i++){
            for(int j=0; j<m; j++){
                if(grid[i][j]==1){
                    if(vis[i][j]==0){
                        count++;
                        int size = bfs(i, j, grid, vis);
                    }
                }
            }
        }

        return count;
    }

    int minDays(vector<vector<int>>& grid) {
        int n=grid.size();
        int m=grid[0].size();
        int maxx = -1e9;
        int count=0;
        vector<vector<int>> vis(n, vector<int>(m, 0));
        int init_count = countIslands(grid);
        if(init_count!=1) return 0;
        for(int i=0; i<n; i++){
            for(int j=0; j<m; j++){
                if(grid[i][j]==1){
                    grid[i][j]=0;
                    int temp = countIslands(grid);
                    if(temp!=1) return 1;
                    grid[i][j]=1;
                }
            }
        }

        return 2;

    }
};

// even number need to remove half except when 2, in that case all
// odd number n-1/2
49100