<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:

    int dx[4]={-1, 0, 1, 0};
    int dy[4]={0, 1, 0, -1};

    void dfs(vector<vector<int>>& grid,vector<vector<bool>> &visited, int i, int j, int n, int m ){
        visited[i][j]= true;
        //grid[i][j]= 2;

        for(int dir=0; dir<4; dir++){
            int newX= i+ dx[dir];
            int newY= j+ dy[dir];

            if(newX>=0 && newX<n && newY>=0 && newY<m &&!visited[newX][newY] && grid[newX][newY] ){
                dfs(grid, visited, newX, newY, n, m );
            }
        }
    }

    int numEnclaves(vector<vector<int>>& grid) {
        int res= 0;

        int n= grid.size();
        int m= grid[0].size();

        vector<vector<bool>> visited(n, vector<bool>(m, false));

        for(int i=0; i<n; i++){
            for(int j=0; j<m; j++){
                if(i==0 || i==n-1 || j==0 || j==m-1 ){
                    if(grid[i][j]==1){
                        dfs(grid, visited, i, j, n, m);
                    }
                }
            }
        }

        for(int i=0; i<n; i++)
            for(int j=0; j<m; j++)
                if(grid[i][j]==1 && !visited[i][j]) res++;
        return res;
    }
};
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