A diagonal of a grid runs from the top-left toward the bottom-right. Given a rectangular grid
grid, return a list containing every diagonal as a list of its values read top-left to bottom-right.
Order the diagonals by their starting cell: begin with the diagonal starting at the top-right corner,
move left along the top row, and then continue down the first column.
Examples
Input: grid = [[1, 2, 3],
[4, 5, 6]]
Output: [[3], [2, 6], [1, 5], [4]]
Input: grid = [[1, 2],
[3, 4]]
Output: [[2], [1, 4], [3]]
Constraints
0 <= rows, cols <= 100; an empty grid gives[]
Goals
- Group cells by the value c - r
- Emit groups in a specified order