<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 ans = 0;
    int n,m;
    bool vs[52][52];

    bool isValid(int l , int k){
        if(l>=0 && l<n && k>=0 && k<m && vs[l][k] == false){
            return true;
        }
        return false;
    }

    vector<pair<int,int>> dr = {{1,0},{-1,0},{0,1},{0,-1}};

    void bfs(int ci , int cj , vector<vector<int>>& grid){
        int current = 1;
        queue<pair<int,int>> qu;
        qu.push({ci,cj});
        vs[ci][cj] = true;

        while(!qu.empty()){
            pair<int,int> crnt = qu.front();
            qu.pop();

            int cri = crnt.first;
            int crj = crnt.second;
            
            for(auto pr: dr){
                int nxi = cri + pr.first;
                int nxj = crj + pr.second;

                if(isValid(nxi,nxj) && grid[nxi][nxj] == 1){
                    current++;
                    vs[nxi][nxj] = true;
                    qu.push({nxi,nxj});
                }
            }
        }
        ans = max(ans,current);
    }

    int maxAreaOfIsland(vector<vector<int>>& grid) {
        n = grid.size();
        m = grid[0].size();
        int i,j;
        memset(vs,false,sizeof(vs));

        for(i=0 ; i<n ; i++){
            for(j=0 ; j<m ; j++){
                if(vs[i][j] == false && grid[i][j] == 1){
                    bfs(i,j,grid);
                }
            }
        }
        return ans;
    }
};
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