Given a grid grid, return all its values in a single list in snake order: the first row from
left to right, the second row from right to left, the third from left to right, and so on.
Examples
Input: grid = [[1, 2, 3],
[4, 5, 6],
[7, 8, 9]]
Output: [1, 2, 3, 6, 5, 4, 7, 8, 9]
Input: grid = [[1, 2],
[3, 4]]
Output: [1, 2, 4, 3]
Constraints
0 <= rows, cols <= 100; an empty grid gives an empty list
Goals
- Alternate the direction of traversal on every row
- Flatten a grid into a single list