<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(int row,int col,vector<vector<int>>&visited,vector<vector<int>>& grid){
        visited[row][col]=1;
        int n=grid.size();
        int m=grid[0].size();
        queue<pair<int,int>>q;
        q.push({row,col});
        int area=1;
        while(!q.empty()){
            auto it=q.front();
            int rrow=it.first;
            int ccol=it.second;
            q.pop();
            vector<int>drow={-1,0,1,0};
            vector<int>dcol={0,1,0,-1};
            for(int i=0;i<4;i++){
                int nrow=rrow+drow[i];
                int ncol=ccol+dcol[i];
                if(nrow>=0 && nrow<n && ncol>=0 && ncol<m && grid[nrow][ncol]==1 && !visited[nrow][ncol]){
                    visited[nrow][ncol]=1;
                    q.push({nrow,ncol});
                    area++;
                }
            }
        }
        return area;
    }
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int n=grid.size();
        int m=grid[0].size();
        int max_area=0;
        vector<vector<int>>visited(n,vector<int>(m,0));
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(grid[i][j]==1 && !visited[i][j]){
                    int ans=bfs(i,j,visited,grid);
                    max_area=max(ans,max_area);
                }
            }
        }
        return max_area;
    }
};
34370