Short Problem Definition:
We define P to be a permutation of the first n natural numbers in the range
[1,n]. Let pos[i] denote the value at position i in permutation P using 1-based indexing.
P is considered to be an absolute permutation if |pos[i]-i| = K holds true for every i.
time complexity is O(N)
space complexity is O(N)
The time complexity of this solution is a question as is always true with hash maps. It is either O(N), O(NlogN) or O(N^2) depending on your particular implementation and hash algorithm.
After I solved this, I looked at the editorial and was amazed by the complex algorithm that they proposed. This is much simpler. Yet I agree that the editorial is more time/space effective.
Iterate over the list of all values [1,N]. Use the lowest available value from the [1,N] pool. Either i-K or i+k, if i-K is not available.
import math import os import random import re import sys # Complete the absolutePermutation function below. def absolutePermutation(n, k): solution =  s = set(range(1,n+1)) for pos in xrange(1, n+1): if pos-k in s: solution.append(pos-k) s.remove(pos-k) elif pos+k in s: solution.append(pos+k) s.remove(pos+k) else: return [-1] return solution if __name__ == '__main__': fptr = open(os.environ['OUTPUT_PATH'], 'w') t = int(raw_input()) for t_itr in xrange(t): nk = raw_input().split() n = int(nk) k = int(nk) result = absolutePermutation(n, k) fptr.write(' '.join(map(str, result))) fptr.write('n') fptr.close()