Python 3   ||   4 lines,  w/ explanation   ||   T/S: 99% / 99%
It\'s easy to show thatn is not the answer if and only if every power of two less thannis innums. A direct result of that fact is the answer is the first power 
It\'s easy to show that`n` is not the answer if and only if every power of two less than`n`is in`nums`. A direct result of that fact is the answer is the first power of 2 not in`nums`is the answer.\n\nIt follows directly from this fact that the answer is the first power of two not in`nums`.\n```\nclass Solution:\n    def minImpossibleOR(self, nums: List[int]) -> int:\n\n        pow2 = 1\n\n        for _ in range(30):\n\n            if pow2 not in nums: return pow2\n\n            pow2*= 2\n\n```\n[https://leetcode.com/problems/minimum-impossible-or/submissions/1296010698/](https://leetcode.com/problems/minimum-impossible-or/submissions/1296010698/)\n\nI could be wrong, but I think that time complexity is *O*(*N*) and space complexity is *O*(1).
['Python3']