leetcode561: Array Partition I

要求：

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: 4Explanation: n is 2, and the maximum sum of pairs is 4 = min(1, 2) + min(3, 4).

Note:

1. n is a positive integer, which is in the range of [1, 10000].
2. All the integers in the array will be in the range of [-10000, 10000].

比较好奇出题的人是怎么想的。。。

public int arrayPairSum(int[] nums) {ArrayList list = new ArrayList();int result = 0;for (int i = 0; i < nums.length; i++)list.add(nums[i]);list.sort(null);for (int i = 0; i < list.size(); i += 2)result += (int) list.get(i);return result;}