<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;
    vector<vector<bool>> vis;
    vector<vector<int>> colr;
    unordered_map<int,int> mp;
    bool check(int row,int col){
        if(row<0 || row>=n || col<0 || col>=m){
            return 0;
        }
        return 1;
    }
    int dx[4] = {0,1,-1,0};
    int dy[4] = {-1,0,0,1};
    void dfs(int color,int row,int col,vector<vector<int>>& grid){
        vis[row][col] = 1;
        colr[row][col] = color;
        mp[color]++;
        for(int i=0;i<4;i++){
            int nx = row+dx[i];
            int ny = col+dy[i];
            if(check(nx,ny) && !vis[nx][ny] && grid[nx][ny]==1){
                dfs(color,nx,ny,grid);
            }
        }
    }
    int maxAreaOfIsland(vector<vector<int>>& grid) {
        n = grid.size();
        m = grid[0].size();
        vis.assign(n,vector<bool>(m,0));
        colr.assign(n,vector<int>(m,0));
        int ans = 0;
        for(int i=0;i<n;i++){
            for(int j=0;j<m;j++){
                if(!vis[i][j] && grid[i][j]==1){
                    ans++;
                    dfs(ans,i,j,grid);
                }
            }
        }
        int res = 0;
        if(ans==0){
            return 0;
        }
        for(auto it:mp){
            res=max(res,it.second);
        }
        return res;
    }
};

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