Given an array of 2n integers, your task is to group these integers into n pairs of integer, say (a1, b1), (a2, b2), …, (an, bn) which makes sum of min(ai, bi) for all i from 1 to n as large as possible.
给出一个长度为 2n 的整数数组，你的任务是将这些整数分成n组，每组两个一对，并求得 所有分组中较小的数 的总和（这个总和的值要尽可能的大）
Input:
[1,4,3,2]
Output: 4
Explanation: n is 2, and the maximum sum of pairs is 4.
Note: n is a positive integer, which is in the range of [1, 10000]. All the integers in the array will be in the range of [-10000, 10000].
思路：将整个数组升序排列，从下标为 0 处开始，每隔两个 取一个，并求和
class Solution(object):
def arrayPartitionI(self, nums):
return sum(sorted(nums)[::
2])
