<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:

void bfs0(vector<vector<int>>& grid, vector<vector<bool>>& v, int x, int y)
{

    queue<pair<int,int>> q;
    q.push({x,y});
    v[x][y]=true;

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

    vector<vector<int>> d = {{1,0}, {-1,0}, {0,1}, {0,-1}};

    while(!q.empty())
    {
        auto a =q.front();
        q.pop();

        for(auto i : d)
        {
            int nx=a.first + i[0];
            int ny=a.second+ i[1];

         if(nx>=0 && ny>=0 && nx <= m-1 && ny <= n-1 && grid[nx][ny]==0 && !v[nx][ny]) 
            {
                    v[nx][ny]=true;
                    q.push({nx,ny});
            }
        }
    }

}

void bfs(vector<vector<int>>& grid, int x,int y, vector<vector<bool>>& v)
{
    queue<pair<int,int>> q;
    q.push({x,y});
    v[x][y]=true;

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

    vector<vector<int>> d = {{1,0}, {-1,0}, {0,1}, {0,-1}};

    while(!q.empty())
    {
        auto a =q.front();
        q.pop();

        for(auto i : d)
        {
            int nx=a.first + i[0];
            int ny=a.second+ i[1];

            if(nx>0 && ny>0 && nx < m-1 && ny < n-1 && grid[nx][ny]==0 && !v[nx][ny]) 
            {
                    v[nx][ny]=true;
                    q.push({nx,ny});
            }
        }
    }
}

    int closedIsland(vector<vector<int>>& grid) {
        int a=0;
        
        int m=grid.size();
        int n=grid[0].size();

        vector<vector<bool>> v(m,vector<bool> (n,false));

        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                if(i==0 || i==m-1 ||j==0 || j==n-1)
                {
                    if(grid[i][j]==0 && !v[i][j])
                    bfs0(grid,v,i,j);
                }
            }
        }

        for(int i=1;i<m-1;i++)
        {
            for(int j=1;j<n-1;j++)
            {          
                if(grid[i][j]==0 && !v[i][j])
                {
                    bfs(grid,i,j,v);
                    a++;
                }
            }
        }

        return a;
    }
};
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