# 1020. Number of Enclaves

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

## Description

You are given an `m x n` binary matrix `grid`, where `0` represents a sea cell and `1` represents a land cell.

A **move** consists of walking from one land cell to another adjacent (**4-directionally**) land cell or walking off the boundary of the `grid`.

Return *the number of land cells in* `grid` *for which we cannot walk off the boundary of the grid in any number of **moves***.

**Example 1:**

![](https://assets.leetcode.com/uploads/2021/02/18/enclaves1.jpg)

```
**Input:** grid = [[0,0,0,0],[1,0,1,0],[0,1,1,0],[0,0,0,0]]
**Output:** 3
**Explanation:** There are three 1s that are enclosed by 0s, and one 1 that is not enclosed because its on the boundary.
```

**Example 2:**

![](https://assets.leetcode.com/uploads/2021/02/18/enclaves2.jpg)

```
**Input:** grid = [[0,1,1,0],[0,0,1,0],[0,0,1,0],[0,0,0,0]]
**Output:** 0
**Explanation:** All 1s are either on the boundary or can reach the boundary.
```

**Constraints:**

* `m == grid.length`
* `n == grid[i].length`
* `1 <= m, n <= 500`
* `grid[i][j]` is either `0` or `1`.

## ac

```java
```