<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, vector<vector<int>>& grid,vector<vector<int>>& vis){
        int m = grid.size(), n = grid[0].size();
        vis[i][j] = 1;
        int drow[] = {-1,0,1,0};
        int dcol[] = {0,-1,0,1};
        for(int ii=0;ii<4;ii++){
            int ni = i+drow[ii];
            int nj = j+dcol[ii];
            if(ni>=0 && ni<m && nj<n && nj>=0 && vis[ni][nj]==-1 && grid[ni][nj]==1) dfs(ni,nj,grid,vis);
        }
    }
    int numEnclaves(vector<vector<int>>& grid) {
        
        int m = grid.size(), n = grid[0].size();
        vector<vector<int>> vis(m,vector<int>(n,-1));
        for(int i=0;i<m;i++){
            if(vis[i][0]==-1 && grid[i][0]==1) dfs(i,0,grid,vis);
            if(vis[i][n-1]==-1 && grid[i][n-1]==1) dfs(i,n-1,grid,vis);
        }
        for(int j=0;j<n;j++){
            if(vis[0][j]==-1 && grid[0][j]==1) dfs(0,j,grid,vis);
            if(vis[m-1][j]==-1 && grid[m-1][j]==1) dfs(m-1,j,grid,vis);
        }
        int res = 0;
        
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                cout<<vis[i][j]<<" ";
                if(vis[i][j]==-1 && grid[i][j]==1) res++;
            }
            cout<<'\n';
        }

        return res;

    }
};
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