Given an $m\times n$ matrix, return an array containing the matrix elements in spiral order, starting from the top-left cell.

Constraints:

• $1\leq$ matrix.length $\leq 10$
• $1\leq$ matrix[i].length $\leq 10$
• $-100\leq$ matrix[i][j] $\leq 100$

The essence of the spiral order traversal algorithm for matrices lies in navigating through the matrix in a spiral pattern—initially moving left-to-right, then top-to-bottom, followed by right-to-left, and finally bottom-to-top, with this cycle repeating until all elements have been visited. ...