I am looking at this challenge:
A function takes a list of numbers, extends that list with the doubles of those numbers and then shuffles the result randomly.
[1,2,4] > [1,2,4,2,4,8] > [8,4,1,2,2,4]
Write a function that takes a potential output list and returns the original list. Return
noneif no such possible original list exists.
[8,4,1,2,2,4] > [1,2,4] [1,4,2] > None
I can see an O(nlogn) solution by sorting and then using a hashmap to keep track of doubles to skip every time you come across a new original number.
Is there a faster solution (perhaps linear)?
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