# Sinking Islands

Given an 2D `matrix`

of `0`

s and `1`

s, a `1`

represents land and `0`

represents water. An island is a group of `1`

’s that are surrounded by `0`

s or by the border. Find all the islands that are completely surrounded by water and modify them into `0`

s.

An island is completed surrounded by water if all of the neighbours are water (that is, none of the neighbours are borders).

Note: Neighbours can only be directly horizontal or vertical, not diagonal.

**Constraints**

`n, m ≤ 250`

where`n`

and`m`

are the number of rows and columns in`matrix`

https://binarysearch.com/problems/Sinking-Islands

## Examples

### Example 1

**Input**

- board =

```
[[1,1],
[1,0]]
```

**Output**

- answer =
`[[1, 1], [1, 0]]`

**Explanation**

The island is not submerged since it touches some of the borders.

### Example 2

**Input**

- board =

```
[[1,0,0,0],
[0,1,1,0],
[0,0,0,0]]
```

**Output**

- answer =
`[[1, 0, 0, 0], [0, 0, 0, 0], [0, 0, 0, 0]]`

**Explanation**

The island in the middle `[(1, 1), (1, 2)]`

is completely submerged.

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