<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>

class Solution:
    def numEnclaves(self, grid: List[List[int]]) -> int:
        rows = len(grid)
        cols = len(grid[0])

        stack = []
        visited = set()
        count = 0

        def isBoundary(row, col):
            if row == 0 or row == rows-1 or col == 0 or col == cols-1:
                return True
            return False

        

        for row in range(rows):
            for col in range(cols):
                if grid[row][col] == 1 and isBoundary(row, col):
                    stack.append((row, col))
                    visited.add((row, col))
        
        while len(stack) != 0:
            row, col = stack.pop()
            directions = [
                (row+1, col),
                (row-1, col),
                (row, col+1),
                (row, col-1),
            ]
            for nextRow, nextCol in directions:
                if nextRow >= 0 and nextRow < rows and nextCol >= 0 and nextCol < cols and (nextRow, nextCol) not in visited and grid[nextRow][nextCol] == 1:
                    stack.append((nextRow, nextCol))
                    visited.add((nextRow, nextCol))


        for row in range(rows):
            for col in range(cols):
                if grid[row][col] == 1 and (row, col) not in visited:
                    count += 1

        return count
25139