<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:
    vector<int> dirs { 0, 1, 0, -1, 0 };

    int size(vector<vector<int>>& grid, vector<vector<bool>>& v, int sr, int sc) { 
        v[sr][sc] = true;
        deque<pair<int, int>> q { {sr, sc} };
        int count = 0;
        while (q.size()) { 
            auto next = q.back(); q.pop_back(); count++;
            for (int i = 0; i < dirs.size() - 1; i++) { 
                int r = dirs[i] + next.first;
                int c = dirs[i + 1] + next.second;
                if (r < 0 || c < 0 || r == grid.size() || c == grid[0].size() || v[r][c] || !grid[r][c]) continue;
                v[r][c] = true;
                // count++;
                q.push_front({ r, c });
            }
        }
        return count;
    }

    int maxAreaOfIsland(vector<vector<int>>& grid) {
        int res = 0;
        vector<vector<bool>> v(grid.size(), vector<bool>(grid[0].size(), false));
        for (int r = 0; r < grid.size(); r++) { 
            for (int c = 0; c < grid[0].size(); c++) { 
                if (grid[r][c] && !v[r][c]) { 
                    res = max(res, size(grid, v, r, c));
                }
            }
        }
        return res;
    }
};
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