TwoSum

Given an array of integers, return indices of the two numbers such that they add up to a specific target.

You may assume that each input would have exactly one solution.

Example:

Given nums = [2, 7, 11, 15], target = 9,

Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].

UPDATE (2016/2/13):
The return format had been changed to zero-based indices. Please read the above updated description carefully.

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解题报告：

扫描给定列表，判断target与扫描到的元素是否出现在自己新建的字典中。如果有，则返回各自下标。如果没有，将该元素加入字典中。

 1 class Solution(object):
 2     def twoSum(self, nums, target):
 3         """
 4         :type nums: List[int]
 5         :type target: int
 6         :rtype: List[int]
 7         """
 8         d = {}
 9         for i in range(len(nums)):
10             if target - nums[i] in d:
11                 return [d[target-nums[i]], i]
12             else:
13                 d[nums[i]] = i