<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 bfs(vector<vector<int>>& grid,vector<vector<int>> &vis,
    int n,int m,int i,int j){
        bool ans=true;
        vis[i][j]=1;
        queue<pair<int,int>> q;
        q.push({i,j});
        while(!q.empty()){
            int row=q.front().first;
            int col=q.front().second;
            //count++;
            q.pop();
            vector<int> vec1{-1,0,1,0};
            vector<int> vec2{0,1,0,-1};
            for(int i=0;i<4;i++){
                int nrow=row+vec1[i];
                int ncol=col+vec2[i];
                if(nrow>=0&&nrow<n&&ncol>=0&&ncol<m&&
                vis[nrow][ncol]==0&&grid[nrow][ncol]==0){
                    if(nrow==0||nrow==n-1||ncol==0||ncol==m-1){
                        ans=false;
                    }
                    vis[nrow][ncol]=1;
                    q.push({nrow,ncol});
                }
            }
        }
        return ans;
    }
    int closedIsland(vector<vector<int>>& grid) {
        int n=grid.size();
        int m=grid[0].size();
        vector<vector<int>> vis(n,vector<int>(m,0));
        int count=0;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(vis[i][j]==0&&grid[i][j]==0&&i!=0&&i!=n-1&&
                j!=0&&j!=m-1){
                    if(bfs(grid,vis,n,m,i,j)){
                        count++;
                    }
                }
            }
        }
        return count;
    }
};
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