<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:
        def dfs(r,c,row,col):
            self.vis.add((r,c))
            for i in range(4):
                left=r+row[i]
                right=c+col[i]
                if left>=0 and left<=len(grid)-1 and right>=0 and right<=len(grid[0])-1 and (left,right) not in self.vis and grid[left][right]==1:
                    dfs(left,right,row,col)

        res=[]
        self.vis=set()
        for i in range(len(grid)):
            for j in range(len(grid[0])):
                if (i==0 or i==len(grid)-1 or j==0 or j==len(grid[0])-1) and grid[i][j]==1:
                    res.append((i,j))
                    self.vis.add((i,j))
        row=[-1,1,0,0]
        col=[0,0,-1,1]
        for r,c in res:
            dfs(r,c,row,col)
        cnt=0
        for i in range(len(grid)):
            for j in range(len(grid[0])):
                if grid[i][j]==1 and (i,j) not in self.vis:
                    cnt+=1
        return cnt

40084