# coding=utf-8
"""
TRIE树py实现

运行速度有点慢啊，用时1000ms，打败10%，估计是`to_bit`和`to_num`耗时了，
改成bit的移位操作应该可以优化，有待于profile考证

~~时间复杂度是O(nlog(m))，m是n的最大位数~~

时间复杂度是O(n)，bit位32写死在程序里面了
"""

from collections import defaultdict
from pprint import pprint

def default_factory():
    return defaultdict(default_factory)

def to_bit(k):
    """1024 -> [0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0]"""
    return (['0']*32+list(bin(k)[2:]))[-32:]
def to_num(k):
    """[0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0] -> 1024"""
    return int(''.join(k),2)
def not_(l):
    return [{'0':'1','1':'0'}[bit] for bit in l]


class TRIE:
    def __init__(self):
        self._root = default_factory()

    def __contains__(self, other):
        node = self._root
        for bit in other:
            if bit not in node:
                return False
            node=node[bit]
        return True


    def add(self, num):
        node = self._root
        for bit in num:
            node = node[bit]
        node['value']=num

    def find_most_closed(self, other):
        node = self._root
        res = []
        for bit in other:
            if bit not in node:
                bit = {'0':'1','1':'0'}[bit]
            node=node[bit]
            res.append(bit)
        assert node['value']==res
        return res

    def freeze(self):
        self._root=dict(self._root)

class Solution(object):
    def findMaximumXOR(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """

        nums = [to_bit(k) for k in nums]

        trie = TRIE()

        for num in nums:
            trie.add(num)

        res=[]
        for num in nums:
            not_num = not_(num)
            r = trie.find_most_closed(not_num)
            r = to_num(r)
            num = to_num(num)
            res.append(num^r)
        return max(res)

s=Solution()
nums = [3, 10, 5, 25, 2, 8]
z=s.findMaximumXOR(nums)
assert z==28