1020. Number of Enclaves

Medium

3.4K

65

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:**

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

**Example 2:**

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

.

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