Spiral Matrix ​
Return all the elements of an m x n matrix in spiral order.
Approach ​
Keep a dx and dy to indicate direction of movement. Ending condition is i >= m*n. Replace the visited element with some garbage.
Remarks ​
https://youtu.be/pLjhGbKMxL4?si=uCEUBkU9Wkx5Y-Jl