<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 {
public:
  vector<vector<bool>>visited;
  void dfs(vector<vector<int>>& board,int i,int j)
    {
         if(i<0||i>board.size()-1||j<0||j>board[0].size()-1)
        return;
        if(board[i][j]!=1)
        return;
       
        if(visited[i][j]==true)
        return;
       
          
        
        visited[i][j]=true;
       dfs(board,i-1,j);
       dfs(board,i+1,j);
       dfs(board,i,j+1);
       dfs(board,i,j-1);
    }
    
    int numEnclaves(vector<vector<int>>& grid) {
         int n=grid.size();
        int m=grid[0].size();
        visited.assign(n, vector<bool>(m, false));
        for(int i=0;i<n;i++)
        {
          dfs(grid,i,0);
          dfs(grid,i,m-1);
        }
         for(int j=0;j<m;j++)
        {
          dfs(grid,0,j);
          dfs(grid,n-1,j);
        }
        int c=0;
        for(int i=0;i<n;i++)
        {
            for(int j=0;j<m;j++)
            {
                if(grid[i][j]==1&&!visited[i][j])
                c++;
            }
        }
        return c;
    }
};
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