```
import math
class Solution(object):
result_x = [0]*31
result_y = [0]*31
highest_x = 0
highest_y = 0
result = 0
def hammingDistance(self, x, y):
if x > 0:
self.highest_x = math.floor(math.log(x, 2))
self.result_x[int(31-self.highest_x-1)] = 1
temp_x = x - 2**self.highest_x
else:
temp_x = 0
if y > 0:
self.highest_y = math.floor(math.log(y, 2))
self.result_y[int(31-self.highest_y-1)] = 1
temp_y = y - 2**self.highest_y
else:
temp_y = 0
if temp_x == 0 and temp_y == 0:
for i in range(31):
if self.result_x[i] != self.result_y[i]:
self.result += 1
return self.result
self.hammingDistance(temp_x, temp_y)
```

First , I get binary code of number and put it into a int list, then i compare two list and find where has different. It is effective on my ide(just as image shows) when we test case (x=3, y=1), but leetcode return a **null**???

so who can tell me where went wrong about my code??

Thanks!