<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(vector<vector<int>>&grid, vector<vector<int>>&vis, int row, int col) {

        vis[row][col] = 1;
        vector<pair<int,int>>dir = {{0, 1}, {1, 0}, {-1, 0}, {0, -1}};
        int m = grid.size();
        int n = grid[0].size();
        for(auto [a,b] : dir) {

            int x = row + a;
            int y = col + b;

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

        for(int j = 0; j < n; j++) {

            if(grid[0][j] == 1 && !vis[0][j]) {
                dfs(grid, vis, 0, j);
            }

            if(grid[m-1][j] == 1 && !vis[m-1][j]) {
                dfs(grid, vis, m-1, j);
            }
        }

        int c = 0;

        for(int i = 0; i < m; i++) {
            for(int j = 0; j < n; j++) {

                if(grid[i][j] == 1 && !vis[i][j])
                    c++;
            }
        }
        return c;
    }
};
55212