<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 {
private: vector<vector<int>> dir = {{-1,0}, {0, -1}, {1,0}, {0,1}};
public:
    void dfs(vector<vector<int>>& grid, int row, int col, vector<vector<int>>& vis){
        vis[row][col]=1;
        for(int i=0; i<4; i++)
        {
            int nrow = row + dir[i][0];
            int ncol = col + dir[i][1];
            if(nrow>=0 && nrow<grid.size() && ncol>=0 && ncol<grid[0].size() && grid[nrow][ncol]==1 && vis[nrow][ncol]==0)
                dfs(grid, nrow, ncol, vis);
        }
    }
    int numEnclaves(vector<vector<int>>& grid) {
        int n=grid.size();
        int m=grid[0].size();
        int ans=0;
        vector<vector<int>> vis(n, vector<int>(m,0));
        for(int i=0; i<n; i++)
            for(int j=0; j<m; j++){
                if(grid[i][j]==0)
                    vis[i][j]=1;
            }
        for(int i=0; i<n; i++)
            if(grid[i][0]==1 )
            {
                dfs(grid,i,0,vis);
            }
        for(int i=0; i<n; i++)
            if(grid[i][m-1]==1 )
            {
                dfs(grid,i,m-1,vis);
            }
        for(int j=0; j<m; j++)
            if(grid[0][j]==1)
            {
                dfs(grid,0,j,vis);
            }
        for(int j=0; j<m; j++)
            if(grid[n-1][j]==1 )
            {
                dfs(grid,n-1,j,vis);
            }
        for(int i=0; i<n; i++)
            for(int j=0; j<m; j++){
                if(vis[i][j]==0 && grid[i][j]==1)
                   ans++; 
            }
        return ans;
    }
};
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