<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:

    void dfs(int i, int j, int m, int n, vector<vector<int>>& grid, vector<vector<int>>& vis, int &count){
        if(i == n || j == m || i<0 || j<0 || grid[i][j] == 0 || vis[i][j] == 1){
            return;
        }
        vis[i][j] = 1;
        count++;

        dfs(i-1, j, m, n, grid, vis, count);
        dfs(i+1, j, m, n, grid, vis, count);
        dfs(i, j-1, m, n, grid, vis, count);
        dfs(i, j+1, m, n, grid, vis, count);

    }

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

        for(int i=0; i<n; i++){
            for(int j=0; j<m; j++){
                if(i==0 || j==0 || i==n-1 || j==m-1 && !vis[i][j] && grid[i][j]){
                    int count = 0;
                    dfs(i ,j, m, n, grid, vis, count);
                    res -= count;
                }
            }
        }
        for(vector<int> it : grid){
            res += count(it.begin(), it.end(), 1);
        }

        return res;
    }
};
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