<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>>& grid, vector<vector<bool>>& visited, int i, int j){
//         visited[i][j] = true;
//         int m = grid.size();
//         int n = grid[0].size();
//         int row_c[] = {-1, 0, 1, 0};
//         int col_c[] = {0, -1, 0, 1};
//         for(int k=0; k<4; k++){
//             int new_row = i + row_c[k];
//             int new_col  = j + col_c[k];
//             if(new_row >= 0 && new_row < m && new_col >= 0 && new_col < n && 
//                 grid[new_row][new_col] == 1 && !visited[new_row][new_col]){
//                 dfs(grid, visited, new_row, new_col);
//             }
//         }
//     }

//     int minDays(vector<vector<int>>& grid) {
//         int m = grid.size();
//         int n = grid[0].size();
//         vector<vector<bool>> visited(m, vector<bool> (n,false));
//         int island = 0;
//         for(int i=0; i<m; i++){
//             for(int j=0; j<n; j++){
//                 if(grid[i][j]==1 && !visited[i][j]){
//                     island++;
//                     dfs(grid, visited, i, j);
//                 }
//             }
//         }

//         if(island != 1){
//             return 0;
//         }


//         for(int k=0; k<m; k++){
//             for(int w=0; w<n; w++){
//                 int new_island = 0;
//                 if(grid[k][w]==1){
//                     vector<vector<int>> grid2 = grid;
//                     grid2[k][w]=0;
//                     vector<vector<bool>> new_visited(m, vector<bool> (n,false));
//                     for(int i=0; i<m; i++){
//                         for(int j=0; j<n; j++){
//                             if(grid2[i][j]==1 && !new_visited[i][j]){
//                                 new_island++;
//                                 dfs(grid2, new_visited, i, j);
//                             }
//                         }
//                     }
//                 }
//                 if(new_island != 1){
//                     return 1;
//                 }
//             }
//         }
//         return 2;
//     }
// };

class Solution {
public:

    void dfs(vector<vector<int>>& grid, vector<vector<bool>>& visited, int i, int j){
        visited[i][j] = true;
        int m = grid.size();
        int n = grid[0].size();
        int row_c[] = {-1, 0, 1, 0};
        int col_c[] = {0, -1, 0, 1};
        for(int k = 0; k < 4; k++){
            int new_row = i + row_c[k];
            int new_col  = j + col_c[k];
            if(new_row >= 0 && new_row < m && new_col >= 0 && new_col < n && 
                grid[new_row][new_col] == 1 && !visited[new_row][new_col]){
                dfs(grid, visited, new_row, new_col);
            }
        }
    }

    int minDays(vector<vector<int>>& grid) {
        int m = grid.size();
        int n = grid[0].size();
        vector<vector<bool>> visited(m, vector<bool> (n, false));
        int island = 0;

        for(int i = 0; i < m; i++){
            for(int j = 0; j < n; j++){
                if(grid[i][j] == 1 && !visited[i][j]){
                    island++;
                    dfs(grid, visited, i, j);
                }
            }
        }

        if(island != 1){
            return 0;
        }

        for(int k = 0; k < m; k++){
            for(int w = 0; w < n; w++){
                if(grid[k][w] == 1){
                    vector<vector<int>> grid2 = grid;
                    grid2[k][w] = 0;  
                    vector<vector<bool>> new_visited(m, vector<bool> (n, false));
                    int new_island = 0;

                    for(int i = 0; i < m; i++){
                        for(int j = 0; j < n; j++){
                            if(grid2[i][j] == 1 && !new_visited[i][j]){
                                new_island++;
                                dfs(grid2, new_visited, i, j);
                            }
                        }
                    }

                    if(new_island != 1){
                        return 1;
                    }
                }
            }
        }

        return 2;
    }
};

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