<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>


class Solution {
public:
  int maximalSquare(vector<vector<char>> &matrix) {
    vector<vector<char>> *otherMatrix = &matrix;

    vector<vector<char>> *currentMatrix = new vector<vector<char>>(
        matrix.size(), vector<char>(matrix[0].size(), 0));

    int maxSquare = 0;
    for(auto chars : matrix) {
        for(char c: chars) {
            if(c == '1') {
                maxSquare = 1;
                break;
            }
        }
    }
    int rowSize = matrix.size();
    int colSize = matrix[0].size();
    int maxSquareSize = min(rowSize, colSize);

    int curSquare = 1;
    while (curSquare < maxSquareSize) {
      // row
      for (int i = 0; i < rowSize - curSquare; i++) {
        for (int j = 0; j < colSize - curSquare; j++) {
          int test = ((*otherMatrix)[i][j] - '0') +
                     ((*otherMatrix)[i + 1][j] - '0') +
                     ((*otherMatrix)[i + 1][j + 1] - '0') +
                     (*otherMatrix)[i][j + 1] - '0';
          if (((*otherMatrix)[i][j] - '0') + ((*otherMatrix)[i + 1][j] - '0') +
                  ((*otherMatrix)[i + 1][j + 1] - '0') +
                  (*otherMatrix)[i][j + 1] - '0' >=
              4) {
            (*currentMatrix)[i][j] = '1';
            if (curSquare + 1 > maxSquare)
              maxSquare = curSquare + 1;
          } else {
            (*currentMatrix)[i][j] = '0';
          }
        }
      }
      curSquare++;
      auto temp = otherMatrix;
      otherMatrix = currentMatrix;
      currentMatrix = temp;
    }
    return maxSquare * maxSquare;
  }
};

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