Update Number of 1 Bits.py

an efficient solution use bitwise operation

Author: resorcap

Number of 1 Bits.py

@@ -1,8 +1,7 @@
 class Solution:
     def hammingWeight(self, n):
-        weight = 0
-        while n != 0:
-            if n%2:
-                weight += 1
-            n = n >> 1
-        return weight
+        count = 0
+        while n:
+            count += 1;
+            n = (n-1)&n
+        return count