<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 x,int y,vector<vector<int>> &vis,vector<vector<int>> &dir,vector<vector<int>>& grid){
        vis[x][y]=1;
        int n=grid.size();
        int m=grid[0].size();
        for(auto &it:dir){
            int newX=x+it[0];
            int newY=y+it[1];
            if(newX>=0 && newX<n && newY>=0 && newY<m && vis[newX][newY]==0 && grid[newX][newY]==1){
                vis[newX][newY]=1;
                dfs(newX,newY,vis,dir,grid);
            }
        }
    }
    int numEnclaves(vector<vector<int>>& grid) {
        int n=grid.size();
        int m=grid[0].size();
        vector<vector<int>> dir={{-1,0},{1,0},{0,-1},{0,1}};
        vector<vector<int>> vis(n,vector<int> (m,0));
        for(int j=0;j<m;j++){
            if(!vis[0][j] && grid[0][j]==1){
                dfs(0,j,vis,dir,grid);
            }
            if(!vis[n-1][j] && grid[n-1][j]==1){
                dfs(n-1,j,vis,dir,grid);
            }
        }
        for(int i=0;i<n;i++){
            if(!vis[i][0] && grid[i][0]==1){
                dfs(i,0,vis,dir,grid);
            }
            if(!vis[i][m-1] && grid[i][m-1]==1){
                dfs(i,m-1,vis,dir,grid);
            }
        }
        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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