<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 n, m;
int a[505][505];
bool vis[505][505];
 bool ans= false;
 vector<pair<int, int>> v = {{0, 1}, {0, -1}, {-1, 0}, {1, 0}};

bool isValid(int i, int j)
{
    if (i >= 0 && i < n && j >= 0 && j < m  )
    {
        return true;
    }

    else
    {
        return false;
    }
}
void dfs(int si, int sj,vector<vector<int>>& grid )
{

    vis[si][sj] = true;
    // cn++;
    if(si==0||si==n-1||sj==0||sj==m-1) {
      ans=false;
    }
    for (int i = 0; i < 4; i++)
    {
        int ci = v[i].first + si;
        int cj = v[i].second + sj;
        if (isValid(ci, cj) && !vis[ci][cj] && grid[ci][cj] == 0)
        {

            dfs(ci, cj,grid);
        }
    }
    // cout<<cn<<" ";
}

  int closedIsland(vector<vector<int>>& grid) {
     
    
         memset(vis, false, sizeof(vis));
         
    vector<int> vec;
    int mx=0;
    n = grid.size();
    m=grid[0].size();
    int result=0;
    for (int i = 0; i < n; i++)
    {
        for (int j = 0; j < m; j++)
        {
            if (vis[i][j] == false &&grid[i][j] == 0 )
            {
                ans = true;
                dfs(i, j,grid);
                if(ans) result++;
               
            }
        }
    }
      return result;
    }
  
};
13450