Description：
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, and you may not use the same element twice.
Translate：
给一组整数，返回两个之和等于给定的特殊目标值的数的索引。
你可以假设每个输入将有一个确切的解决方案，但您不能使用相同元素的两次。
Example:
Given nums = [2, 7, 11, 15], target = 9,
Because nums[0] + nums[1] = 2 + 7 = 9,
return [0, 1].
Solution：
class Solution(object):
def twoSum(self, nums, target):
if len(nums) <= 1:
return False
buff_dict = {}
for i in range(len(nums)):
if nums[i] in buff_dict:
return [buff_dict[nums[i]], i]
else:
buff_dict[target - nums[i]] = i
by：https://leetcode.com/problems/two-sum/discuss/17
Analysis：
