An integer array
original is transformed into a doubled array
changed by appending twice the value of every element in
original, and then randomly shuffling the resulting array.
Given an array
changed is a doubled array. If
changed is not a doubled array, return an empty array. The elements in
original may be returned in any order.
Input: changed = [1,3,4,2,6,8] Output: [1,3,4] Explanation: One possible original array could be [1,3,4]: - Twice the value of 1 is 1 * 2 = 2. - Twice the value of 3 is 3 * 2 = 6. - Twice the value of 4 is 4 * 2 = 8. Other original arrays could be [4,3,1] or [3,1,4].
Input: changed = [6,3,0,1] Output:  Explanation: changed is not a doubled array.
Input: changed =  Output:  Explanation: changed is not a doubled array.
1 <= changed.length <= 105
0 <= changed[i] <= 105