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

        int cnt = 0;

        queue<pair<int,int>> q;
        set<pair<int,int>> vis;

        for(int i=0;i<m;i++)
        {   
            for(int j=0;j<n;j++)
            {
                if(grid[i][j]==1)
                {
                    cnt++;
                    if(i==0 || i==m-1 || j==0
                    ||j==n-1)
                    {
                        q.push({i,j});
                        vis.insert({i,j});
                    }
                }
            }
        }

        vector<vector<int>> moves = {{1,0},{-1,0},{0,1},{0,-1}};
        while(!q.empty())
        {
            int x = q.front().first;
            int y = q.front().second;
            q.pop();
            
            for(auto dir : moves)
            {
                int new_x = x+dir[0];
                int new_y = y+dir[1];

                if(new_x>=0 && new_x<m && new_y>=0&&
                new_y<n && vis.count({new_x,new_y})==0 &&
                grid[new_x][new_y]==1)
                {
                    q.push({new_x,new_y});
                    vis.insert({new_x,new_y});
                }
            }   
            cnt--;
        }

        return cnt; 
    }
};
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