<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 {
private:
    void dfs(vector<vector<int>>& image,int a,int b,int color,int ini,int m,int n){
        vector<pair<int,int>>dir={{0,1},{0,-1},{1,0},{-1,0}};
        for(auto it:dir){
            int newX=a+it.first;
            int newY=b+it.second;
            if(newX>=0 && newY>=0 && newX<m && newY<n && image[newX][newY]==ini && image[newX][newY]!=color){
                image[newX][newY]=color;
                dfs(image,newX,newY,color,ini,m,n);
            }
        }
    }
public:
    int numEnclaves(vector<vector<int>>& grid) {
        int m=grid.size();
        int n=grid[0].size();
        int color=2;
        int ini=1;
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                if((i==0 || j==0 || i==m-1 || j==n-1) && grid[i][j]==ini){
                    grid[i][j]=color;
                    dfs(grid,i,j,color,ini,m,n);
                }
            }
        }
        int cnt=0;
        for(int i=0;i<m;i++){
            for(int j=0;j<n;j++){
                if(grid[i][j]==1){
                    cnt++;
                }
            }
        }
        return cnt;
}};
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