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;

    }

}