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.
Example 1: 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].
就是把数字两两配对，然后每对里面小的加起来要最大
思路：
把小的分一组，这样就可以尽消耗掉小的数字，使总的结果更大
如 min（1，2）+min（3，4） = 1+3=4
code：
class Solution(object):
def arrayPairSum(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
return sum(sorted(nums)[::2])
