<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 vis[305][305]={false};  
    int bfs(vector<vector<int>>& grid, int i,int j){
        queue <int>q1;
        queue <int>q2;
        q1.push(i);
        q2.push(j);
        vis[i][j]=1;
        int isOK=1;
        while(!q1.empty()){
            int a=q1.front();q1.pop();
            int b=q2.front();q2.pop();
            if(a-1>=0){
                if(grid[a-1][b]==0 && !vis[a-1][b]){
                    vis[a-1][b]=1;
                    q1.push(a-1);q2.push(b);
                }
            }
            else isOK =0;
            if(b-1>=0){
                if(grid[a][b-1]==0 && !vis[a][b-1]){
                    vis[a][b-1]=1;
                    q1.push(a);q2.push(b-1);
                }
            }
            else isOK =0;
            if(a+1<grid.size()){
                if(grid[a+1][b]==0 && !vis[a+1][b]){
                    vis[a+1][b]=1;
                    q1.push(a+1);q2.push(b);
                }
            }
            else isOK =0;
            if(b+1<grid[0].size()){
                if(grid[a][b+1]==0 && !vis[a][b+1]){
                    vis[a][b+1]=1;
                    q1.push(a);q2.push(b+1);
                }
            }
            else isOK =0;
        }
        return isOK;

    }
    int closedIsland(vector<vector<int>>& grid) {
        int cnt=0;
        for (int i=0;i<grid.size();i++){
            for (int j=0;j<grid[i].size();j++){
                if(grid[i][j]==0 && !vis[i][j]){
                    auto isClosed=bfs(grid,i,j);
                    if(isClosed){
                        cnt++;
                    }
                }
            }
        }
        return cnt;
    }
};
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