leetcode 561 数组拆分

561 这道题花里胡哨的，直接排序，取下标为奇数的加一起求和就行了。

class Solution(object):
    def arrayPairSum(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        nums.sort()
        return sum(nums[i] for i in range(0, len(nums), 2))

605 这道题只要前面数、当前数和后面数都为0，就把当前数设置为1，遍历过去！！！最伟大的地方在于在起始和终止都添加一个0，看评论说这叫防御式编程思想！！！

class Solution(object):
    def canPlaceFlowers(self, flowerbed, n):
        """
        :type flowerbed: List[int]
        :type n: int
        :rtype: bool
        """
        flowerbed.append(0)
        flowerbed.insert(0, 0)
        flowers = 0
        for i in range(1, len(flowerbed)-1):
            if flowerbed[i] == 0 and flowerbed[i-1] == 0 and flowerbed[i+1] == 0:
                flowerbed[i] = 1
                flowers += 1
        return n <= flowers