<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:
    int closedIsland(vector<vector<int>>& grid) {

        int ans = 0;
        int n =grid.size();
        int m=grid[0].size();

        for(int i=0;i<m;i++) {
            if(grid[0][i]==0)
                dfs(grid,0,i);
        }
        for(int i=0;i<n;i++) {
            if(grid[i][0]==0)
                dfs(grid,i,0);
        }

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

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

        for(int i=0;i<n;i++) {
            for(int j=0;j<m;j++) {
                if(grid[i][j]==0) {
                    cout<<i<<" "<<j<<"\n";
                    dfs(grid,i,j);
                    ans++;
                }
            }
        }
        return ans;
        
    }

    void dfs(vector<vector<int>> &grid, int i,int j) {
        if(i<0 || j<0 || i>=grid.size() || j>=grid[0].size() || grid[i][j]!=0)
            return;
        grid[i][j]=1;
        vector<pair<int,int>> dr = {{1,0},{-1,0},{0,1},{0,-1}};
        for(int k=0;k<4;k++) {
            int a = i+dr[k].first;
            int b = j+dr[k].second;
            dfs(grid,a,b);
        }
    }
};
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