<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 {
    void dfs(vector<vector<int>>& board,vector<vector<int>>& vis,int row,int col){
        vector<int>dr={-1,1,0,0};
        vector<int>dc={0,0,-1,1};
        vis[row][col]=1;
        int n=board.size();
        int m=board[0].size();

        for(int i=0;i<4;i++){
            int nrow=row+dr[i];
            int ncol=col+dc[i];

            if(nrow>=0 && nrow<n && ncol>=0 && ncol<m && board[nrow][ncol]==1 &&
            vis[nrow][ncol]!=1){
                dfs(board,vis,nrow,ncol);
            }
        }

        
    }
public:
    int numEnclaves(vector<vector<int>>& grid) {
        int n=grid.size();
        int m=grid[0].size();
        vector<vector<int>>vis(n,vector<int>(m,0));

        for(int i=0;i<n;i++){
            if(grid[i][0]==1 && vis[i][0]!=1){
                
                dfs(grid,vis,i,0);
            }
            if(grid[i][m-1]==1 && vis[i][m-1]!=1){
                
                dfs(grid,vis,i,m-1);
            }


        }
        for(int j=0;j<m;j++){
            if(grid[0][j]==1 && vis[0][j]!=1){
                
                dfs(grid,vis,0,j);
            }
            if(grid[n-1][j]==1 && vis[n-1][j]!=1){
                
                dfs(grid,vis,n-1,j);
            }

        }
        int count=0;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(vis[i][j]==0 && grid[i][j]==1){
                    count++;
                }
            }
        }

        return count;

        
    }
};
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