leetcode-grind/problems/561/problem.txt

 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 = min(1, 2) + min(3, 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].