[Leetcode] 561. Array Partition I 解題報告

題目：

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:

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].

思路：

練手題目，哈哈。首先對nums排序，然後将其奇數索引下的數加起來即可。

代碼：

class Solution {
public:
    int arrayPairSum(vector<int>& nums) {
        sort(nums.begin(), nums.end());
        int ret = 0;
        for (int i = 0; i < nums.size(); i +=2) {
            ret += nums[i];
        }
        return ret;
    }
};