<p>Given a 2D&nbsp;<code>grid</code> consists of <code>0s</code> (land)&nbsp;and <code>1s</code> (water).&nbsp; An <em>island</em> is a maximal 4-directionally connected group of <code><font face="monospace">0</font>s</code> and a <em>closed island</em>&nbsp;is an island <strong>totally</strong>&nbsp;(all left, top, right, bottom) surrounded by <code>1s.</code></p>

<p>Return the number of <em>closed islands</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2019/10/31/sample_3_1610.png" style="width: 240px; height: 120px;" /></p>

<pre>
<strong>Input:</strong> grid = [[1,1,1,1,1,1,1,0],[1,0,0,0,0,1,1,0],[1,0,1,0,1,1,1,0],[1,0,0,0,0,1,0,1],[1,1,1,1,1,1,1,0]]
<strong>Output:</strong> 2
<strong>Explanation:</strong> 
Islands in gray are closed because they are completely surrounded by water (group of 1s).</pre>

<p><strong class="example">Example 2:</strong></p>

<p><img alt="" src="https://assets.leetcode.com/uploads/2019/10/31/sample_4_1610.png" style="width: 160px; height: 80px;" /></p>

<pre>
<strong>Input:</strong> grid = [[0,0,1,0,0],[0,1,0,1,0],[0,1,1,1,0]]
<strong>Output:</strong> 1
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> grid = [[1,1,1,1,1,1,1],
&nbsp;              [1,0,0,0,0,0,1],
&nbsp;              [1,0,1,1,1,0,1],
&nbsp;              [1,0,1,0,1,0,1],
&nbsp;              [1,0,1,1,1,0,1],
&nbsp;              [1,0,0,0,0,0,1],
               [1,1,1,1,1,1,1]]
<strong>Output:</strong> 2
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>1 &lt;= grid.length, grid[0].length &lt;= 100</code></li>
	<li><code>0 &lt;= grid[i][j] &lt;=1</code></li>
</ul>

class Solution {
    void dfs(int row,int col, vector<vector<int>>&visited,vector<vector<int>>& grid){
        int n = grid.size();
        int m = grid[0].size();
        visited[row][col] = 1;
        vector<pair<int,int>>directions= {{-1,0},{0,1},{1,0},{0,-1}};
        for(auto &dir:directions){
            int nrow = row+dir.first;
            int ncol = col+dir.second;

             if(nrow >= 0 && nrow < n && ncol >= 0 && ncol < m && !visited[nrow][ncol] && grid[nrow][ncol] == 0){
                dfs(nrow,ncol,visited,grid);
             }
        }
        return;
    }
public:
    int closedIsland(vector<vector<int>>& grid) {
        int n = grid.size();
        int m = grid[0].size();
        vector<vector<int>>visited(n,vector<int>(m,0));
        queue<pair<int,int>>q;

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

        for(int i = 0; i < n ;i++){
            if(grid[i][0] == 0 && !visited[i][0]){
                dfs(i,0,visited,grid);
            }
            if(grid[i][m-1] == 0 && !visited[i][m-1]){
                dfs(i,m-1,visited,grid);
            }
        }
        /*vector<pair<int,int>>directions= {{-1,0},{0,1},{1,0},{0,-1}};
        while(!q.empty()){
            int row = q.front().first;
            int col = q.front().second;

            q.pop();
            
            for(auto &dir:directions){
                int nrow = row+dir.first;
                int ncol = col+dir.second;

                if(nrow >= 0 && nrow < n && ncol >= 0 && ncol < m && !visited[nrow][ncol] && grid[nrow][ncol] == 0){
                    visited[nrow][ncol] == 1;
                    q.push({nrow,ncol});
                }
            }
        }*/
        int count = 0;
        for(int i =0;i<n;i++){
            for(int j=0;j<m;j++){
                if(!visited[i][j] && grid [i][j] == 0){
                    dfs(i,j,visited,grid);
                    count++;
                }
            }
        }

        return count;
    }
};
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