<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 bfs(vector<vector<int>>& grid,int i,int j,vector<vector<int>>&vis,int n,int m) {
        queue<pair<int,int>>q;
        vis[i][j]=1;
        int x[]={-1,0,1,0};int y[]={0,1,0,-1};
        q.push({i,j});
        while(!q.empty()) {
            int r=q.front().first,c=q.front().second;
            q.pop();
            for(int i=0;i<4;i++) {
                int newr=r+x[i],newc=c+y[i];
                if(newr>=0 && newr<n && newc>=0 && newc<m) {
                    if(!vis[newr][newc] && grid[newr][newc]==0) {
                        vis[newr][newc]=1;
                        q.push({newr,newc});
                    }
                }
            }
        }
        return ;
    }

    int closedIsland(vector<vector<int>>& grid) {
        int n=grid.size(),m=grid[0].size();
        vector<vector<int>>vis(n,vector<int>(m,0));
        queue<pair<int,int>>q;
        for(int i=0;i<n;i++) {
            for(int j=0;j<m;j++) {
                if(!vis[i][j] && grid[i][j]==0 && (i==n-1 || i==0 || j==0 || j==m-1)) {
                    vis[i][j]=1;
                    q.push({i,j});
                }
            }
        }
        int x[]={-1,0,1,0};int y[]={0,1,0,-1};
        while(!q.empty()) {
            int r=q.front().first,c=q.front().second;
            q.pop();
            for(int i=0;i<4;i++) {
                int newr=r+x[i],newc=c+y[i];
                if(newr>=0 && newr<n && newc>=0 && newc<m) {
                    if(!vis[newr][newc] && grid[newr][newc]==0) {
                        vis[newr][newc]=1;
                        q.push({newr,newc});
                    }
                }
            }
        }
        for(int i=0;i<n;i++) {
            for(int j=0;j<m;j++) {
                cout<<vis[i][j]<<" ";
            }
            cout<<endl;
        }
        int ans=0;
        for(int i=0;i<n;i++) {
            for(int j=0;j<m;j++) {
                if(!vis[i][j] && grid[i][j]==0) {
                    ans++;
                    bfs(grid,i,j,vis,n,m) ;
                }   
            }
        }
        // for(int i=0;i<n;i++) {
        //     for(int j=0;j<m;j++) {
        //         cout<<vis[i][j]<<" ";
        //     }
        //     cout<<endl;
        // }
        return ans;
    }
};
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