<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>

#include <bits/stdc++.h>
using namespace std;
class Solution {
    private:
    void bfs(vector<vector<int>>& grid,vector<vector<bool>> &vis,int sr,int sc){
        int n=grid.size();
        int m=grid[0].size();
        queue<pair<int,int>> q;
        if(grid[sr][sc]==1){
            q.push({sr,sc});
            vis[sr][sc]=true;
        }
        while(!q.empty()){
            int x=q.front().first;
            int y=q.front().second;
            q.pop();
            if(x>0 && vis[x-1][y]==false && grid[x-1][y]==1){
                q.push({x-1,y});
                vis[x-1][y]=true;
            }
            if(y>0 && vis[x][y-1]==false && grid[x][y-1]==1){
                q.push({x,y-1});
                vis[x][y-1]=true;
            }
            if(x<n-1 && vis[x+1][y]==false && grid[x+1][y]==1){
                q.push({x+1,y});
                vis[x+1][y]=true;
            }
            if(y<m-1 && vis[x][y+1]==false && grid[x][y+1]==1){
                q.push({x,y+1});
                vis[x][y+1]=true;
            }
        }
    }
    public:
        int numEnclaves(vector<vector<int>>& grid){
            int n=grid.size();
            int m=grid[0].size();
            vector<vector<bool>> vis(n,vector<bool> (m,false));
            int ans=0;
            for(int i=0;i<n;i++){
                bfs(grid,vis,i,0);
            }
            for(int i=0;i<n;i++){
                bfs(grid,vis,i,m-1);
            }
            for(int i=0;i<m;i++){
                bfs(grid,vis,0,i);
            }
            for(int i=0;i<m;i++){
                bfs(grid,vis,n-1,i);
            }
            for(int i=0;i<n;i++){
                for(int j=0;j<m;j++){
                    if(grid[i][j]==1 && vis[i][j]==false){
                        ans++;
                    }
                }
            }
            return ans;
    
        }
    };
39042