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1020. 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:
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:
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 either0
or1
.