561. Array Partition I

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].

自己的代码

public class Solution {
    public int ArrayPairSum(int[] nums) {
       List<int> ai = new List<int>();
            for (int i = 0; i < nums.Length; i++)
            {
                ai.Add(nums[i]);
            }
            ai.Sort();
            List<int> sumai = new List<int>();
            int min = 10000;
            if (ai.Count == 2)
            {
                sumai.Add(ai[0]);
            }
            else
            {
                for (int i = 0; i < ai.Count; i++)
                {
                    if (i%2==0)
                    {
                        sumai.Add(ai[i]);
                    }
                }
            }
            int sums=0;
        foreach(int i in sumai)
        {
            sums+=i;
        }
        return sums;
    }
}