class Solution(object):
    def findMaximumXOR(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        max,mask=0,0
        
        for i in range(31,-1,-1): 
            mask|=(1<<i)
            prefix_set=set()
            for num in nums:
                prefix_set.add(num&mask)
            temp=max|(1<<i)
            for prefix in prefix_set:
                if temp^prefix in prefix_set:
                    max=temp
                    break
        return max
        

class Solution(object):
    def findMaximumXOR(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        answer=0
        for i in range(31,-1,-1):
            answer<<=1
            prefixes={num>>i for num in nums}
            answer+=any(answer^1^prefix in prefixes for prefix in prefixes)
        return answer