<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 n, m;
    bool isValid(int i, int j){
        if(i>=0 && i<n && j>=0 && j<m) return true;
        return false;
    }
    void dfs(int i, int j, vector<vector<int>>& grid){
        grid[i][j]=0;
        vector<pair<int, int>> dir={{0,1}, {1,0}, {-1,0}, {0,-1}};
        for(int k=0; k<4; k++){
            int row = i + dir[k].first;
            int col = j + dir[k].second;
            if(isValid(row,col) && grid[row][col]==1){
                dfs(row, col,  grid);
            }
        }
        
    }
    int numEnclaves(vector<vector<int>>& grid) {
        n = grid.size();
        m = grid[0].size();
        int count =0;
        for(int i=0;i<n; i++){
            for(int j = 0; j<m; j++){
                if((i*j==0 || i==n-1 || j==m-1) && grid[i][j]==1){
                    dfs(i, j, grid);
                }
            }
        }
        for(int i=1;i<n-1; i++){
            for(int j = 1; j<m-1; j++){
                if(grid[i][j]==1){
                    count++;
                }
            }
        }
        return count;
    }
};
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