<p>You are given an <code>m x n</code> binary matrix <code>grid</code>, where <code>0</code> represents a sea cell and <code>1</code> represents a land cell.</p>

<p>A <strong>move</strong> consists of walking from one land cell to another adjacent (<strong>4-directionally</strong>) land cell or walking off the boundary of the <code>grid</code>.</p>

<p>Return <em>the number of land cells in</em> <code>grid</code> <em>for which we cannot walk off the boundary of the grid in any number of <strong>moves</strong></em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/enclaves1.jpg" style="width: 333px; height: 333px;" />
<pre>
<strong>Input:</strong> grid = [[0,0,0,0],[1,0,1,0],[0,1,1,0],[0,0,0,0]]
<strong>Output:</strong> 3
<strong>Explanation:</strong> There are three 1s that are enclosed by 0s, and one 1 that is not enclosed because its on the boundary.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/02/18/enclaves2.jpg" style="width: 333px; height: 333px;" />
<pre>
<strong>Input:</strong> grid = [[0,1,1,0],[0,0,1,0],[0,0,1,0],[0,0,0,0]]
<strong>Output:</strong> 0
<strong>Explanation:</strong> All 1s are either on the boundary or can reach the boundary.
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == grid.length</code></li>
	<li><code>n == grid[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 500</code></li>
	<li><code>grid[i][j]</code> is either <code>0</code> or <code>1</code>.</li>
</ul>

from collections import deque
class Solution:
    def numEnclaves(self, grid: List[List[int]]) -> int:
        q = deque()
        directions = [
            (-1,0), #up
            (0,1), #right
            (1,0), #down
            (0,-1) #left
        ]
        
        res = set()
        ROWS = len(grid)
        COLS = len(grid[0])

        for r in [0,ROWS-1]:
            for c in range(COLS):
                if grid[r][c] == 1:
                    q.append((r,c))
        
        for c in [0,COLS-1]:
            for r in range(ROWS):
                if grid[r][c] == 1:
                    q.append((r,c))

        visited = set()
        while q:
            snapshot = len(q)
            for _ in range(snapshot):
                r,c = q.popleft()
                res.add((r,c))
                for dr,dc in directions:
                    nr,nc = r + dr,c+dc
                    if (0 <= nr < ROWS and
                            0 <= nc < COLS and
                            grid[nr][nc] == 1 and
                            (nr,nc) not in visited):
                            q.append((nr,nc))
                            visited.add((nr,nc))
        
        
        for r,c in res:
            grid[r][c] = 0
        
        land = 0
        for r in range(ROWS):
            for c in range(COLS):
                if grid[r][c] == 1:
                    land += 1
        return land
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