Given a rectangular grid grid, return the values on its border in clockwise order, starting at
the top-left corner: along the top row, down the right column, back along the bottom row, and up the
left column. Every border cell appears exactly once.
Examples
Input: grid = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]
Output: [1, 2, 3, 6, 9, 8, 7, 4]
Input: grid = [[1, 2, 3]]
Output: [1, 2, 3]
Input: grid = [[1],
[2],
[3]]
Output: [1, 2, 3]
Constraints
1 <= rows, cols <= 100
Goals
- Traverse the outer ring of a grid in clockwise order
- Avoid repeating corner cells and handle a single row or column