Fix time complexity notation in Compute Alternating Sum

Updated time complexity notation to O(n + n).

Author: 724thomas

leetcode3/최원준/3701. Compute Alternating Sum.py

@@ -0,0 +1,16 @@
+#
+
+'''
+1. 아이디어 :
+
+
+2. 시간복잡도 :
+    O(n + n)
+
+3. 자료구조/알고리즘 :
+
+
+'''
+class Solution:
+    def alternatingSum(self, nums: List[int]) -> int:
+        return sum([nums[i] if i%2==0 else -nums[i] for i in range(len(nums))])