561. Array Partition I

题目：给定一个序列有2n个数，目标是把它们分成n组，（ai,bi）,使得ai和bi中较小的那个的所有的加和最大，输出这个值。

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].

思路：排序，将奇数位的数相加
class Solution {
public:
int arrayPairSum(vector<int>& nums) {
sort(nums.begin(),nums.end());
int n=nums.size();
if(n%2) return 0;
int sum=0;
for(int i=0;i<n;i++)
{
sum+=nums[i];
i++;

}
return sum;
}
};