<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 {
public:
bool dfs(int i,int j,vector<vector<int>>& grid,vector<vector<int>>&vis){
    if(i==0 || j==0 || i==grid.size()-1 || j==grid[0].size()-1){
        return false;
    }
    vis[i][j]=1;
    bool isClosed = true;

    vector<int>dr={0,-1,0,1};
    vector<int>dc={-1,0,1,0};
    for(int k=0;k<4;k++){
        int nr=i+dr[k];
        int nc=j+dc[k];
        if(nc>=0&&nr>=0&&nc<grid[0].size()&&nr<grid.size()&&vis[nr][nc]==-1&&grid[nr][nc]==0){
            if(dfs(nr,nc,grid,vis)==false){
                isClosed= false;
            }
        }
        
    }
    return isClosed;
}
    int closedIsland(vector<vector<int>>& grid) {
        int count=0;
        int n=grid.size();
        int m=grid[0].size();
        vector<vector<int>>vis(n,vector<int>(m,-1));
        
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(grid[i][j]==0 && vis[i][j]==-1){
                    if(dfs(i,j,grid,vis)==true){
                        count++;
                    }
                }
            }
        }
        return count;
    }
};
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