```
class Solution(object):
def isReflected(self, points):
"""
:type points: List[List[int]]
:rtype: bool
"""
if not points: return True
s=max(points, key=lambda x:x[0])[0]+min(points, key=lambda x:x[0])[0]
m=s/2.0
right=set()
reflected=set()
for x,y in points:
if x>m: # right of m
right.add((x,y))
elif x<m: # left of m, reflect it
reflected.add((s-x,y))
return right==reflected
```