<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 bfs(int idx, int jdx, vector<vector<int>> &visited, vector<vector<int>> &grid){
        int n = grid.size();
        int m = grid[0].size();

        queue<pair<int,int>> q;

        visited[idx][jdx] = 1;

        q.push({idx,jdx});

        int arr[4][2] = {{0,1},{1,0},{-1,0},{0,-1}};

        while(!q.empty()){
            int ie = q.front().first;
            int je = q.front().second;
            q.pop();

            for(int i = 0;i<4;i++){
            int ci = ie + arr[i][0];
            int cj = je + arr[i][1];

            if(ci>=0 && ci<n && cj>=0 && cj<m && visited[ci][cj]==0 && grid[ci][cj]==1){
                visited[ci][cj] = 1;
                q.push({ci,cj});
            }
        }
        }
        

        return;
    }

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

        vector<vector<int>> visited(n, vector<int> (m,0));

        for(int i = 0;i<n;i++){
            if(!visited[i][0] && grid[i][0]==1){
                bfs(i,0,visited, grid);
            }
            if(!visited[i][m-1] && grid[i][m-1]==1){
                bfs(i,m-1,visited, grid);
            }
        }

        for(int j = 0;j<m;j++){
            if(!visited[0][j] && grid[0][j]==1){
                bfs(0,j,visited, grid);
            }
            if(!visited[n-1][j] && grid[n-1][j]==1){
                bfs(n-1,j,visited, grid);
            }
        }

        for(int i = 0;i<n;i++){
            for(int j = 0;j<m;j++){
                if(grid[i][j] == 1 && visited[i][j] == 0){
                    cnt++;
                }
            }
        }

        return cnt;
    }
};
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