Print a Matrix in Diagonal Order

Question

## Interview Question: Print a Matrix in Diagonal Order

Given a 2D matrix of size m × n, design a function that prints (or returns) all elements of the matrix in **diagonal order**, where each diagonal runs from the top-left toward the bottom-right (i.e., traversing the matrix along its slanted / diagonal lines).

### Example
For the matrix:
[
  [1, 2, 3],
  [4, 5, 6],
  [7, 8, 9]
]

The expected diagonal output is:
1

2, 4

3, 5, 7

6, 8

9

### Requirements
1. Handle both square and rectangular matrices.
2. Maintain correct traversal order for all diagonals.
3. Provide the time and space complexity of your algorithm.
4. Explain how you determine the start and end of each diagonal.

### Follow-up
How would your solution change if the matrix were extremely large and stored on disk rather than in memory?

Accepted Answer

A detailed reference solution is available to Crack ML Interview members.