Python O(N^2)
```\nclass Solution:\n    def recoverArray(self, nums: List[int]) -> List[int]:\n        n = int(len(nums) / 2)\n        nums.sort()        \n        \n        
```\nclass Solution:\n    def recoverArray(self, nums: List[int]) -> List[int]:\n        n = int(len(nums) / 2)\n        nums.sort()        \n        \n        for i in range(1, n * 2):\n            k = nums[i] - nums[0]\n            if k != 0 and not k % 2:\n                higher = collections.defaultdict(int)\n                original = []\n                for num in nums:\n                    if num in higher and higher[num]:\n                        higher[num] -= 1\n                    else:\n                        higher[num + k] += 1\n                        original.append(num + int(k / 2))\n                if len(original) == n:\n                    return original
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