<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>

#define ppi pair<int,int>
class Solution {
public:
    int m,n;
    vector<ppi> dir={{0,1} ,{0,-1} ,{1,0} ,{-1,0}};
    unordered_set<string> visited;
    string trr(int i,int j)
    {
        return to_string(i)+"."+to_string(j);
    }
    int bfs(int a,int b,vector<vector<int>>& grid)
    {
        int area=0;
        queue<ppi> q;
        //initialization
        q.push({a,b});
        visited.insert(trr(a,b));

        //bfs
        while(!q.empty())
        {
            int i=q.front().first,j=q.front().second;
            q.pop();

            //neighbour check
            for(auto x:dir)
            {
                int r= i+x.first;
                int c= j+x.second;
                if(r<0 || c<0 || r>=m || c>=n) continue;
                if(grid[r][c]==1 && visited.find(trr(r,c)) == visited.end())
                {
                    area++;
                    q.push({r,c});
                    visited.insert(trr(r,c));
                }
            }
        }
        return area+1;
    }
    int maxAreaOfIsland(vector<vector<int>>& grid) 
    {
        m=grid.size();
        n=grid[0].size();
        int maxx=0;
        for(int i=0;i<m;i++)
        {
            for(int j=0;j<n;j++)
            {
                if(grid[i][j]==1 && visited.find(trr(i,j)) == visited.end())
                {
                    //bfs chalegaa
                    maxx=max(maxx,bfs(i,j,grid));
                }
            }
        }
        return maxx;
    }
};
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