[C#][LeetCode][Easy] 561. Array Partition I

問題：

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.

心得：
看到這題我第一個反應就是去找linq有沒有辦法分割陣列，然後再加總= =
不過LINQ效能沒有很好，看到最佳解答有提供一個不錯的方法。

我的答案：

public class Solution {
    public int ArrayPairSum(int[] nums) {
        return nums.OrderBy(x => x)
                   .Select((x, index) => new { index, x })
                   .GroupBy(x => x.index / 2)
                   .Sum(x => x.Select(y => y.x).Min());
    }
}

最佳解答：

public class Solution {
    public int ArrayPairSum(int[] nums) {
        Array.Sort(nums);
        int result = 0;
        for (int i = 0; i < nums.Length; i += 2)
        {
            result += nums[i];
        }
        return result;
    }
}