1254. Number of Closed Islands
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Given a 2D `grid` consists of `0s` (land) and `1s` (water).  An island is a maximal 4-directionally connected group of `0s` and a closed island is an island totally (all left, top, right, bottom) surrounded by `1s.`

Return the number of closed islands.

Example 1:

```Input: 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]]
Output: 2
Explanation:
Islands in gray are closed because they are completely surrounded by water (group of 1s).```

Example 2:

```Input: grid = [[0,0,1,0,0],[0,1,0,1,0],[0,1,1,1,0]]
Output: 1
```

Example 3:

```Input: grid = [[1,1,1,1,1,1,1],
[1,0,0,0,0,0,1],
[1,0,1,1,1,0,1],
[1,0,1,0,1,0,1],
[1,0,1,1,1,0,1],
[1,0,0,0,0,0,1],
[1,1,1,1,1,1,1]]
Output: 2
```

Constraints:

• `1 <= grid.length, grid[0].length <= 100`
• `0 <= grid[i][j] <=1`
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