Create number-of-1-bits.py

kamyu104 · kamyu104 · commit a74fdffab75f · 2015-03-10T22:56:17.000+08:00
diff --git a/Python/number-of-1-bits.py b/Python/number-of-1-bits.py
@@ -0,0 +1,24 @@
+# Time:  O(m)
+# Space: O(1)
+#
+# Write a function that takes an unsigned integer 
+# and returns the number of &rsquo;1' bits it has (also known as the Hamming weight).
+# 
+# For example, the 32-bit integer &rsquo;11' has binary representation 00000000000000000000000000001011, 
+# so the function should return 3.
+#
+# Credits:
+# Special thanks to @ts for adding this problem and creating all test cases.
+#
+class Solution:
+    # @param n, an integer
+    # @return an integer
+    def hammingWeight(self, n):
+        result = 0
+        while n:
+            n &= n - 1
+            result += 1
+        return result
+
+if __name__ == '__main__':
+  print Solution().hammingWeight(11)
