Modify the Matrix
<p>Given a <strong>0-indexed</strong> <code>m x n</code> integer matrix <code>matrix</code>, create a new <strong>0-indexed</strong> matrix called <code>answer</code>. Make <code>answer</code> equal to <code>matrix</code>, then replace each element with the value <code>-1</code> with the <strong>maximum</strong> element in its respective column.</p>

<p>Return <em>the matrix</em> <code>answer</code>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/3000-3099/3033.Modify%20the%20Matrix/images/matrix1.png" style="width: 491px; height: 161px;" />
<pre>
<strong>Input:</strong> matrix = [[1,2,-1],[4,-1,6],[7,8,9]]
<strong>Output:</strong> [[1,2,9],[4,8,6],[7,8,9]]
<strong>Explanation:</strong> The diagram above shows the elements that are changed (in blue).
- We replace the value in the cell [1][1] with the maximum value in the column 1, that is 8.
- We replace the value in the cell [0][2] with the maximum value in the column 2, that is 9.
</pre>

<p><strong class="example">Example 2:</strong></p>
<img alt="" src="https://fastly.jsdelivr.net/gh/doocs/leetcode@main/solution/3000-3099/3033.Modify%20the%20Matrix/images/matrix2.png" style="width: 411px; height: 111px;" />
<pre>
<strong>Input:</strong> matrix = [[3,-1],[5,2]]
<strong>Output:</strong> [[3,2],[5,2]]
<strong>Explanation:</strong> The diagram above shows the elements that are changed (in blue).
</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>2 &lt;= m, n &lt;= 50</code></li>
	<li><code>-1 &lt;= matrix[i][j] &lt;= 100</code></li>
	<li>The input is generated such that each column contains at least one non-negative integer.</li>
</ul>
Array; Matrix
public class Solution {
    public int[][] ModifiedMatrix(int[][] matrix) {
        int m = matrix.Length, n = matrix[0].Length;
        for (int j = 0; j < n; ++j) {
            int mx = -1;
            for (int i = 0; i < m; ++i) {
                mx = Math.Max(mx, matrix[i][j]);
            }
            for (int i = 0; i < m; ++i) {
                if (matrix[i][j] == -1) {
                    matrix[i][j] = mx;
                }
            }
        }
        return matrix;
    }
}