<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:
    def closedIsland(self, grid: List[List[int]]) -> int:
        closed = 0
        visited = set()
        for i in range(len(grid)):
            for j in range(len(grid[i])):
                if grid[i][j] == 0 and (i,j) not in visited:
                    if self.markIsland(grid, [(i,j)], visited, True):
                        closed += 1
                        
        return closed

    def markIsland(self, grid, explore, visited, is_closed):
        while explore:
            i,j = explore.pop()
            visited.add((i,j))
            if i == 0 or i == len(grid) - 1 or j == 0 or j == len(grid[i])- 1:
                is_closed = False
            if i != 0 and grid[i-1][j] == 0 and (i-1,j) not in visited:
                explore.append((i-1,j))
            if i != len(grid) - 1 and grid[i+1][j] == 0 and (i+1,j) not in visited:
                explore.append((i+1,j))
            if j != 0 and grid[i][j-1] == 0 and (i, j-1) not in visited:
                explore.append((i,j-1))
            if j != len(grid[i]) - 1 and grid[i][j+1] == 0 and (i,j+1) not in visited:
                explore.append((i,j+1))

        return is_closed
        
17800