Create sort-integers-by-the-number-of-1-bits.py

Author: kamyu104

Python/sort-integers-by-the-number-of-1-bits.py

@@ -0,0 +1,18 @@
+# Time:  O(nlogn)
+# Space: O(1)
+
+class Solution(object):
+    def sortByBits(self, arr):
+        """
+        :type arr: List[int]
+        :rtype: List[int]
+        """
+        def popcount(n):  # Time: O(logn) ~= O(1) if n is a 32-bit number
+            result = 0
+            while n:
+                n &= n - 1
+                result += 1
+            return result
+        
+        arr.sort(key=lambda x: (popcount(x), x))
+        return arr