<p>Given an <code>m x n</code> matrix <code>mat</code>, return <em>an array of all the elements of the array in a diagonal order</em>.</p>

<p>&nbsp;</p>
<p><strong class="example">Example 1:</strong></p>
<img alt="" src="https://assets.leetcode.com/uploads/2021/04/10/diag1-grid.jpg" style="width: 334px; height: 334px;" />
<pre>
<strong>Input:</strong> mat = [[1,2,3],[4,5,6],[7,8,9]]
<strong>Output:</strong> [1,2,4,7,5,3,6,8,9]
</pre>

<p><strong class="example">Example 2:</strong></p>

<pre>
<strong>Input:</strong> mat = [[1,2],[3,4]]
<strong>Output:</strong> [1,2,3,4]
</pre>

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

<ul>
	<li><code>m == mat.length</code></li>
	<li><code>n == mat[i].length</code></li>
	<li><code>1 &lt;= m, n &lt;= 10<sup>4</sup></code></li>
	<li><code>1 &lt;= m * n &lt;= 10<sup>4</sup></code></li>
	<li><code>-10<sup>5</sup> &lt;= mat[i][j] &lt;= 10<sup>5</sup></code></li>
</ul>

class Solution:
    
    def findDiagonalOrder(self, matrix: List[List[int]]) -> List[int]:
        total_rows, total_cols = len(matrix), len(matrix[0])
        row, column = 0, 0
        direction = 1 # 1 - upwards, 0 - downwards
        result = []
        while row < total_rows and column < total_cols:
            result.append(matrix[row][column])
            
            new_row = row + (-1 if direction == 1 else 1)
            new_column = column + (1 if direction == 1 else -1)
            if not(0 <= new_row < total_rows and 0 <= new_column < total_cols):
                if direction:  #try right then down
                    row += (column == total_cols - 1)
                    column += (column < total_cols - 1)
                else: # try down then right
                    column += (row == total_rows - 1)
                    row += (row < total_rows - 1)
                    
                direction = 1 - direction        
            else:
                row = new_row
                column = new_column
                        
        return result                 
19300