Create alternating-digit-sum.py

Author: kamyu104

Python/alternating-digit-sum.py

@@ -0,0 +1,17 @@
+# Time:  O(logn)
+# Space: O(1)
+
+# math
+class Solution(object):
+    def alternateDigitSum(self, n):
+        """
+        :type n: int
+        :rtype: int
+        """
+        result = 0
+        sign = 1
+        while n:
+            sign *= -1
+            result += sign*(n%10)
+            n //= 10
+        return sign*result