<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 {
    private:
    void dfs(int row,int col,vector<vector<int>>&vis,vector<vector<int>>&grid){
        vis[row][col]=1;
        vector<pair<int,int>>dir={{1,0},{0,1},{-1,0},{0,-1}};
        for(int i=0;i<4;++i){
            int nrow = row+dir[i].first;
            int ncol = col+dir[i].second;
            if(nrow>=0 && nrow<grid.size() && ncol>=0 && ncol<grid[0].size() && !vis[nrow][ncol] && grid[nrow][ncol]==0){
                  dfs(nrow,ncol,vis,grid);
            }
        }
    }
public:
    int closedIsland(vector<vector<int>>& grid) {
        int m = grid.size(), n = grid[0].size(),ct=0;
        vector<vector<int>>vis(m,vector<int>(n,0));
        for(int i=0;i<m;++i){
            if(grid[i][0]==0 && !vis[i][0]){
                dfs(i,0,vis,grid);
            }
            if(grid[i][n-1]==0 && !vis[i][n-1]){
                dfs(i,n-1,vis,grid);
            }
        }
        for(int i=0;i<n;++i){
            if(grid[0][i]==0 && !vis[0][i]){
                 dfs(0,i,vis,grid);
            }
            if(grid[m-1][i]==0 && !vis[m-1][i] ){
                 dfs(m-1,i,vis,grid);
            }
        }
        for(int row=1;row<m-1;++row){
            for(int col=1;col<n-1;++col){
                if(grid[row][col]==0 && !vis[row][col]){
                    ct++;
                    dfs(row,col,vis,grid);
                }
            }
        }
           return ct;
    }
};
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