We have strings of format A_ _ _ _ _ _ _, an A followed by 6 spaces that can be a number 0-9. We also have regular expressions with the operations "or" and "*" defined as follows:. The easiest way to illustrate this is to give an example. "A000001 or A000000" has size 2 because it matches two strings. "*" represents a wild card, so A00000* has size 10 because it matches 10 different strings, (A000000 - A000009). "A0* or A1*" has size 20,000 because it matches 20,000 different strings. The question was this: Write a function that takes in a number N and outputs a regular expression that matches exactly N strings of format A _ _ _ _ _ _.

Given an array of integers and an int k, rotate every element inside the array to the right by k units. Do this in O(n) time and O(1) space. I proposed a O(kn) solution, but that was not good enough. They want the very best solution.