<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(queue<pair<pair<int,int>,int>>&q,vector<vector<int>>&vis,vector<vector<int>>& grid,int isl,int n,int m) {
        int x[]={-1,0,1,0};int y[]={0,1,0,-1};
        while(!q.empty()) {
            int r=q.front().first.first,c=q.front().first.second,cnt=q.front().second;
            q.pop();
            for(int i=0;i<4;i++) {
                int newr=r+x[i],newc=c+y[i];
                if(newr>=0 && newr<n && newc>=0 && newc<m) {
                    if(!vis[newr][newc] && grid[newr][newc]==1) {
                        vis[newr][newc]=1;
                        q.push({{newr,newc},cnt+1});
                        isl++;
                    }
                }
            }
        }
        return isl;
    }

    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int n=grid.size(),m=grid[0].size();
        vector<vector<int>>vis(n,vector<int>(m,0));
        vector<vector<int>>ans(n,vector<int>(m,0));
        queue<pair<pair<int,int>,int>>q;
        int cnt=0;
        for(int i=0;i<n;i++) {
            for(int j=0;j<m;j++) {
                if(grid[i][j]==1 && !vis[i][j]) {
                    q.push({{i,j},1});
                    vis[i][j]=1;
                    int isl=1;
                    int ans=bfs(q,vis,grid,isl,n,m);
                    cnt=max(cnt,ans);
                }
            }
        }
        
        return cnt;
    }
};
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