Day 468

Good morning! Here's your coding interview problem for today.

This problem was asked by Facebook.

Given an `N` by `N` matrix, rotate it by 90 degrees clockwise.

For example, given the following matrix:
```
[[1, 2, 3],
 [4, 5, 6],
 [7, 8, 9]]
```
you should return:
```
[[7, 4, 1],
 [8, 5, 2],
 [9, 6, 3]]
```
Follow-up: What if you couldn't use any extra space?