<p>You are given an <code>m x n</code> binary matrix <code>grid</code>. An island is a group of <code>1</code>&#39;s (representing land) connected <strong>4-directionally</strong> (horizontal or vertical.) You may assume all four edges of the grid are surrounded by water.</p>

<p>The <strong>area</strong> of an island is the number of cells with a value <code>1</code> in the island.</p>

<p>Return <em>the maximum <strong>area</strong> of an island in </em><code>grid</code>. If there is no island, return <code>0</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/05/01/maxarea1-grid.jpg" style="width: 500px; height: 310px;" />
<pre>
<strong>Input:</strong> grid = [[0,0,1,0,0,0,0,1,0,0,0,0,0],[0,0,0,0,0,0,0,1,1,1,0,0,0],[0,1,1,0,1,0,0,0,0,0,0,0,0],[0,1,0,0,1,1,0,0,1,0,1,0,0],[0,1,0,0,1,1,0,0,1,1,1,0,0],[0,0,0,0,0,0,0,0,0,0,1,0,0],[0,0,0,0,0,0,0,1,1,1,0,0,0],[0,0,0,0,0,0,0,1,1,0,0,0,0]]
<strong>Output:</strong> 6
<strong>Explanation:</strong> The answer is not 11, because the island must be connected 4-directionally.
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> grid = [[0,0,0,0,0,0,0,0]]
<strong>Output:</strong> 0
</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;= 50</code></li>
	<li><code>grid[i][j]</code> is either <code>0</code> or <code>1</code>.</li>
</ul>

class Solution {
public:
    int bfs(deque<pair<int, int>> &adj, vector<vector<int>> &vis, vector<vector<int>>& grid, int area){
        int x[4] = {1, -1, 0, 0};
        int y[4] = {0, 0, 1, -1};
        int xn, yn;
        while(!adj.empty()){
            auto now = adj.front();
            adj.pop_front();
            for(auto i =0;i<4;i++){
                xn = now.first+x[i];
                yn = now.second+y[i];
                // cout<<"checking ("<<xn<< yn<<")"<<endl;
                if(xn>=0&&xn<grid.size()&&yn>=0&&yn<grid[0].size()){
                    // cout<<"checking ("<<xn<< yn<<")"<<endl;
                    if(grid[xn][yn]==1&&vis[xn][yn]==0){
                        area++;
                        vis[xn][yn] = 1;
                        adj.push_back({xn, yn});
                    }
                }
            }
        }
        return area;
    }
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int m = grid.size(), n = grid[0].size();
        deque<pair<int, int>> adj;
        int ans=0;
        vector<vector<int>> vis(m, vector<int>(n, 0));

        int island = 0;
        for(auto i =0;i<m;i++){
            for(auto j = 0; j<n; j++){
                // cout<<"checking x"<<i<<"y"<<j<<endl;
                
                if(vis[i][j]==0&&grid[i][j]==1){
                    adj.push_back({i, j});
                    vis[i][j] = 1;
                    ans = max(bfs(adj, vis, grid, 1), ans);
                }
            }
        }
        return ans;
    }
};
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