# 1254. Number of Closed Islands

<https://leetcode.com/problems/number-of-closed-islands>

## Description

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:**

![](https://assets.leetcode.com/uploads/2019/10/31/sample_3_1610.png)

```
**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:**

![](https://assets.leetcode.com/uploads/2019/10/31/sample_4_1610.png)

```
**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`

## ac

```java
```