The problem is https://leetcode.com/problems/maximum-xor-of-two-numbers-in-an-array/. If just follow the process defined as described in problem, it is quite simple except the runtime is O(n**2):

```
class Solution(object):
def findMaximumXOR(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
if len(nums)<2:
return 0
ret = nums[0]^nums[1]
for i in range(len(nums)-1):
for j in range(i+1, len(nums)):
tmp = nums[i]^nums[j]
if tmp > ret:
ret = tmp
return ret
```

And as expected, the result is "time limit exceeded".