LEETCODE - Pair Sum

def arrayPairSum(self, nums:list[int]) -> int:
    sum = 0
    pair = []
    nums.sort()

    for n in nums:
        pair.append(n)
        if len(pair) == 2:
            sum += min(pair)
            pair = []

    return sum

def arrayPairSum2(self, nums:list[int]) -> int:
    sum = 0
    nums.sort()

    for i, n in enumerate(nums):
        if i % 2 == 0 :
            sum += n

    return sum

def arrayPairSum3(self, nums:list[int]) -> int :
    return sum(sorted(nums)[::2])