<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) {
        vector<vector<bool>>vis(grid.size() , vector<bool>(grid[0].size()));
        int n = grid.size();
        int m =grid[0].size();
        int count=0;
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<m;j++)
            {
                if(grid[i][j] == 0 && !vis[i][j] && solve(i , j, n ,m , grid , vis))
                {
                    count++;
                }
            }
        }
        return count;
    }
    bool solve(int x , int y , int n , int m, vector<vector<int>>& grid , vector<vector<bool>>& vis)
    {
        if(x<0 || x>=n || y<0 || y>=m)
        {
            return false;
        }
        if(grid[x][y] == 1 || vis[x][y])
        {
            return true;
        }
        vector<int> dirx {0, 1, 0, -1};
        vector<int> diry {-1, 0, 1, 0};
        vis[x][y] = true;
        bool isClosed = true;
        for(int i=0;i<4;i++)
        {
            int r = x+dirx[i];
            int c = y+diry[i];
            if(!solve(r , c , n,m ,grid, vis))
            {
                isClosed = false;
            }
        }
        return isClosed;
    }
};

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