<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 {
private:
    int n,m;
    bool border(int x,int y){
        if(x==0 || y==0 || x==n-1 || y==m-1){
            return true;
        }
        return false;
    }
    bool check(int x,int y){
        if(x>=0 && y>=0 && x<=n-1 && y<=m-1){
            return true;
        }
        return false;
    }
    
    bool bfs(int x,int y, vector<vector<int>>& grid){
    bool status=true;
    vector<vector<int>> direc{{1,0},{0,1},{-1,0},{0,-1}};
    // grid[x][y]=1;
    if(border(x,y)) status=false;
    queue<pair<int,int>> q;
    q.push({x,y});
    while(!q.empty()){
        int i=q.front().first;
        int j=q.front().second;
        grid[i][j]=1;
        q.pop();

        for(auto& it: direc){
            int a=i+it[0];
            int b=j+it[1];

            if(check(a,b) && grid[a][b]==0){
                q.push({a,b});
                if(border(a,b)) status=false;
            }

        }
    }
    return status;

        
    }
public:
    int closedIsland(vector<vector<int>>& grid) {
        n=grid.size();
        m=grid[0].size();
        int island=0;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(grid[i][j]==0){
                    if(bfs(i,j,grid)) island++;
                }
            }
        }
        return island;
    }
};
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