<p>Given an <code>m x n</code> binary <code>matrix</code> filled with <code>0</code>&#39;s and <code>1</code>&#39;s, <em>find the largest square containing only</em> <code>1</code>&#39;s <em>and return its area</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/26/max1grid.jpg" style="width: 400px; height: 319px;" />
<pre>
<strong>Input:</strong> matrix = [[&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;,&quot;0&quot;],[&quot;1&quot;,&quot;0&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;],[&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;,&quot;1&quot;],[&quot;1&quot;,&quot;0&quot;,&quot;0&quot;,&quot;1&quot;,&quot;0&quot;]]
<strong>Output:</strong> 4
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2020/11/26/max2grid.jpg" style="width: 165px; height: 165px;" />
<pre>
<strong>Input:</strong> matrix = [[&quot;0&quot;,&quot;1&quot;],[&quot;1&quot;,&quot;0&quot;]]
<strong>Output:</strong> 1
</pre>

<p><strong class="example">Example 3:</strong></p>

<pre>
<strong>Input:</strong> matrix = [[&quot;0&quot;]]
<strong>Output:</strong> 0
</pre>

<p>&nbsp;</p>
<p><strong>Constraints:</strong></p>

<ul>
	<li><code>m == matrix.length</code></li>
	<li><code>n == matrix[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 300</code></li>
	<li><code>matrix[i][j]</code> is <code>&#39;0&#39;</code> or <code>&#39;1&#39;</code>.</li>
</ul>

int maximal_square(std::vector<std::vector<char>> const &grid) {
    auto const n = grid[0].size();
    std::vector<int> result(grid.size() * n);
    int max = 0;
    {
        for (auto j = 0uz; j < grid[0].size(); ++j) {
            if (grid[0uz][j] == '1') {
                max = 1;
                result[j] = 1;
            } else {
                result[j] = 0;
            }
        }
        for (auto i = 1uz; i < grid.size(); ++i) {
            if (grid[i][0uz] == '1') {
                max = 1;
                result[i * n] = 1;
            } else {
                result[i * n] = 0;
            }
        }
    }
    for (auto i = 1uz; i < grid.size(); ++i) {
        for (auto j = 1uz; j < grid[i].size(); ++j) {
            if (grid[i][j] == '0') {
                result[i * n + j] = 0;
                continue;
            }

            int left = result[i * n + j - 1uz];
            int top = result[(i - 1uz) * n + j];
            int mid = result[(i - 1uz) * n + j - 1uz];

            int count = 1 + std::min(std::min(left, top), mid);
            max = std::max(max, count);
            result[i * n + j] = count;
        }
    }
    return max * max;
}

class Solution {
public:
    int maximalSquare(vector<vector<char>>& matrix) {
        return maximal_square(matrix);
    }
};
24300