Most of you are familiar with the merge sort algorithm for sorting a list of numbers.
As part of the algorithm, one writes a helper function called
merge that combines two sorted lists into one sorted list.
In Python-like pseudocode, the function usually looks something like this:
function merge(A, B): C =  while A is not empty or B is not empty: if A is empty: C.append(B.pop()) else if B is empty or A ≤ B: C.append(A.pop()) else: C.append(B.pop()) return C
The idea is to keep popping the smaller of the first elements of
B until both lists are empty, and collect the results into
B are both sorted, then so is
C is a sorted list, and we split it into any two subsequences
B are also sorted and
merge(A, B) == C.
Interestingly, this does not necessarily hold if
C is not sorted, which brings us to this challenge.
Your input is a permutation of the first
2*n nonnegative integers
[0, 1, 2, ..., 2*n-1] for some
n > 0, given as a list
Your output shall be a truthy value if there exist two lists
B of length
n such that
C == merge(A, B), and a falsy value otherwise.
Since the input contains no duplicates, you don't have to worry about how ties are broken in the
Rules and Bonuses
You can write either a function or a full program. The lowest byte count wins, and standard loopholes are disallowed.
Note that you are not required to compute the lists
B in the "yes" instances.
However, if you actually output the lists, you receive a bonus of -20%.
To claim this bonus, you must output only one pair of lists, not all possibilities.
To make this bonus easier to claim in strongly typed languages, it is allowed to output a pair of empty lists in the "no" instances.
Brute forcing is not forbidden, but there is a bonus of -10% for computing all of the last four test cases in under 1 second total.
Only one possible output is given in the "yes" instances.
[1,0] -> False [0,1] ->   [3,2,1,0] -> False [0,3,2,1] -> False [0,1,2,3] -> [0,1] [2,3] [1,4,0,3,2,5] -> False [4,2,0,5,1,3] -> [4,2,0] [5,1,3] [3,4,1,2,5,0] -> [4,1,2] [3,5,0] [6,2,9,3,0,7,5,1,8,4] -> False [5,7,2,9,6,8,3,4,1,0] -> False [5,6,0,7,8,1,3,9,2,4] -> [6,0,8,1,3] [5,7,9,2,4] [5,3,7,0,2,9,1,6,4,8] -> [5,3,7,0,2] [9,1,6,4,8] [0,6,4,8,7,5,2,3,9,1] -> [8,7,5,2,3] [0,6,4,9,1] [9,6,10,15,12,13,1,3,8,19,0,16,5,7,17,2,4,11,18,14] -> False [14,8,12,0,5,4,16,9,17,7,11,1,2,10,18,19,13,15,6,3] -> False [4,11,5,6,9,14,17,1,3,15,10,12,7,8,0,18,19,2,13,16] -> [4,17,1,3,15,10,12,7,8,0] [11,5,6,9,14,18,19,2,13,16] [9,4,2,14,7,13,1,16,12,11,3,8,6,15,17,19,0,10,18,5] -> [9,4,2,16,12,11,3,8,6,15] [14,7,13,1,17,19,0,10,18,5]