Jolly Jumper Sequence A sequence of n > 0 integers is called a jolly jumper if the absolute values of the difference between successive elements take on all the values 1 through n-1.

So the sequence [4,1,2,4] has absolute differences [3,1,2] which is equivalent to the set [1,2,3] (1 to n-1 where n is the length of original sequence) so it is therefore a jolly jumper.

Sequences have length n>0.

Assume n=1 is a jolly jumper.

Easy mode: Don't worry about stdin/stdout. Just a function that accepts arguments however and returns something that indicates jolly or not

Hard mode: Input on stdin (space separated), and output is "Jolly" / "Not jolly". Capitalization matters.

This is code golf.

EDIT: Sequences can contain negative integers and input on stdin is space separated.

$ jolly 2 -1 0 2
Jolly

$ jolly 19 22 24 25
Jolly

$ jolly 19 22 24 21
Not jolly
Haskell
Easy 4 characters
Returns a list of jolly integers if and only if a list of jolly integers is given as input. This is legal based on &quot;Just a function that accepts arguments however and returns something that indicates jolly or not&quot;.
j=id

Alternative easy solution with 61 characters:
Takes in a list and returns the empty list if the sequence is jolly.
import List
j n=zipWith(\x-&gt;abs.(x-))n(tail n)\\[1..length n]