2007. Find Original Array From Doubled Array

https://leetcode.com/problems/find-original-array-from-doubled-array

Description

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, return original if 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.

Example 1:

**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].

Example 2:

**Input:** changed = [6,3,0,1]
**Output:** []
**Explanation:** changed is not a doubled array.

Example 3:

**Input:** changed = [1]
**Output:** []
**Explanation:** changed is not a doubled array.

Constraints:

• 1 <= changed.length <= 105

• 0 <= changed[i] <= 105

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