Problem Statement

A doubled array changed is formed from the original array after appending twice the value of each element in the original array and randomly shuffling elements in the updated original array.

Given an array changed, return the original array if changed is a valid doubled array. Otherwise, return empty array.

Examples

• Example 1:

  • Input: changed = [2,4,1,8]
  • Expected Output: [1,4]
  • Justification: The original array [1,4] is doubled to form [2,4,1,8] (1's double is 2, and 4's double is 8).

• Example 2:

  • Input: changed = [6,3,0,0]
  • Expected Output: [0,3]
  • Justification: The original array [0,3] is doubled to form [6,3,0,0] (0's double is 0, and 3's double is 6).

• Example 3:

  • Input: changed = [1, 2, 2, 4, 4, 8, 16, 32]
  • Expected Output: [1, 2, 4, 16]
  • Justification: The original array [1, 2, 4, 16] is doubled to form [1, 2, 2, 4, 4, 8, 16, 32] (1's double is 2, 2's double is 4, 4's double is 8, and 16's double is 32).

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