<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 row,int col,vector<vector<int>>&visited){
        int n=visited.size();
        int m=visited[0].size();
        visited[row][col]=0;
        queue<pair<int,int>>q;
        q.push({row,col});
        while(!q.empty()){
            auto it=q.front();
            int rrow=it.first;
            int ccol=it.second;
            q.pop();
            vector<int>drow={-1,0,1,0};
            vector<int>dcol={0,1,0,-1};
            for(int i=0;i<4;i++){
                int nrow=rrow+drow[i];
                int ncol=ccol+dcol[i];
                if(nrow>=0 && nrow<n && ncol>=0 && ncol<m && visited[nrow][ncol]==1){
                    q.push({nrow,ncol});
                    visited[nrow][ncol]=0;
                }
            }
        }
    }
    int numEnclaves(vector<vector<int>>& grid) {
        int n=grid.size();
        int m=grid[0].size();
        vector<vector<int>>visited=grid;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(visited[i][j]==1 && (i==0 || j==0 || i==n-1 || j==m-1)){
                    bfs(i,j,visited);
                }
            }
        }
        int count=0;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(visited[i][j]==1){
                   count++;
                }
            }
        }
        return count;
        
    }
};
40967