So the idea for this solution is dependent upon the fact the best possible scenario would be for the resulting array b to be have the smallest possible difference of 1 Then iterate through the differences till the second last element

A false statement would be
1 _ 3
Consisting of 3 elements
now the most idealistic difference would be _ to 3 as 1
so 1 2 3, But as the difference between 
2 - 1 == 3 - 2 -> This results in a false statement 

Input: 100 200 4
Output: 
100 _ _ 200
100 _ 199 200
100 197 199 200
And as 197 - 100 > 199 - 197 -> This solution is valid

You can do this by deque

The questions are not difficult if understood, this rank is easy. As long as you are able to understand the question !