<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:
        ROWS, COLS = len(grid), len(grid[0])
        dr = [[0,1],[0,-1],[1,0],[-1,0]]

        seen = set()
        def dfs1(r, c):
            seen.add((r, c))
            grid[r][c] = 1

            for d in dr:
                row = r + d[0]
                col = c + d[1]
                if (row >= 0 and row < ROWS and 
                    col >= 0 and col < COLS and
                    (row, col) not in seen and
                    grid[row][col] == 0):
                    dfs1(row, col)
        
        for r in range(ROWS):
            for c in range(COLS):
                if (c == 0 or c == COLS - 1 or
                    r == 0 or r == ROWS - 1):
                    if (grid[r][c] == 0):
                        dfs1(r, c)

        seen = set()
        def dfs2(r, c):
            seen.add((r, c))
            for d in dr:
                row = r + d[0]
                col = c + d[1]
                if (row >= 0 and row < ROWS and 
                    col >= 0 and col < COLS and
                    (row, col) not in seen and
                    grid[row][col] == 0):
                    dfs2(row, col)
        
        res = 0
        for r in range(ROWS):
            for c in range(COLS):
                if (r, c) not in seen and grid[r][c] == 0:
                    dfs2(r, c)
                    res += 1
        
        return res

        


        
18300