<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 cnt=0;
    bool vis[1005][1005]={false};
    int flag=0;

    bool valid(int i, int j,int row, int col){
    if (i >= 0 && i<row && j>=0 && j<col)return true;
    else return false;
    }

    void bfs(vector<vector<int>>& grid,int si, int sj){
        int row = grid.size();
        int col = grid[0].size();
        
        vector<pair<int, int>> xy = {{-1, 0}, {0, 1}, {1, 0}, {0, -1}};

        queue<pair<int,int>>q;
        q.push({si,sj});
        vis[si][sj]=true;
        while(!q.empty()){
            pair<int,int>node=q.front(); q.pop();
            int r= node.first;
            int c= node.second;
            for(auto child : xy){
                int i=r+child.first;
                int j=c+child.second;
                if(!valid(i,j,row,col)){
                    cout<<i<<" "<<j<<endl;
                    flag=1;
                }
                if(valid(i,j,row,col) && !vis[i][j] && grid[i][j]==0){
                    q.push({i,j});
                    vis[i][j]=true;
                }
            }
        }
        if(flag == 1)cnt--;
        flag=0;
    }
    int closedIsland(vector<vector<int>>& grid) {
        int row = grid.size();
        int col = grid[0].size();
        for(int i=0; i<row; i++){
            for(int j=0; j<col; j++){
                if(grid[i][j]==0 && !vis[i][j]){
                    cnt++;
                    bfs(grid,i,j);
                }
            }
        }
    return cnt;  
    }
};
19010