feature: two sum revisit

arrays/TwoSum.py

@@ -1,10 +1,12 @@
+import collections
 from typing import List
 
 
 # O(n) time || O(n) space
 def two_sum(self, nums: List[int], target: int) -> List[int]:
-    dic = {}
+    dic = collections.defaultdict(int)
     for i, num in enumerate(nums):
         if target - num in dic:
-            return [dic[target - num], i]
+            return [i, dic[target - num]]
+
         dic[num] = i

arrays/test/test_two_sum.py

@@ -5,13 +5,13 @@
 
 class MyTestCase(unittest.TestCase):
     def test_two_sum(self):
-        self.assertEqual([0, 1], two_sum(self, [2, 7, 11, 15], 9))
+        self.assertEqual([1, 0], two_sum(self, [2, 7, 11, 15], 9))
 
     def test_two_sum_1(self):
-        self.assertEqual([1, 2], two_sum(self, [3, 2, 4], 6))
+        self.assertEqual([2, 1], two_sum(self, [3, 2, 4], 6))
 
     def test_two_sum_2(self):
-        self.assertEqual([0, 1], two_sum(self, [3, 3], 6))
+        self.assertEqual([1, 0], two_sum(self, [3, 3], 6))
 
 
 if __name__ == '__main__':