Add solution for leetcode twoSum-2

Author: wisdom08

two-sum/wisdom08.py

@@ -1,6 +1,9 @@
 class Solution:
     def twoSum(self, nums: List[int], target: int) -> List[int]:
-        for i in range(len(nums)-1):
-            for j in range(i+1, len(nums)):
-                if nums[i] + nums[j] == target:
-                    return [i, j]
+        dict = {}
+        for i, v in enumerate(nums):
+            diff = target - v
+            if diff in dict:
+                return [i, dict[diff]]
+            else:
+                dict[v] = i