<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 n,m;
int mx;
int ans;
bool vis[55][55];
vector<pair<int,int>>d={{0,1},{0,-1},{1,0},{-1,0}};
bool valid(int i,int j){
    if(i>=0 && i<n && j>=0 && j<m) return true;
    else return false;
}


void dfs(int si,int sj,vector<vector<int>>&grid){
    vis[si][sj]=true;
    ans++;
    for(int i=0;i<4;i++){
        int ci=si+d[i].first;
        int cj=sj+d[i].second;
        if(valid(ci,cj)&&  !vis[ci][cj] && grid[ci][cj]==1){
            dfs(ci,cj,grid);
        }
    }
}
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        n=grid.size();
m=grid[0].size();
mx=0;
for(int i=0;i<n;i++){
    for(int j=0;j<m;j++){
        if( !vis[i][j] && grid[i][j]==1){
            ans=0;
            dfs(i,j,grid);
            mx=max(mx,ans);
        }
    }
}
return mx;
    }
};


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