开始写数组了！！！
直接遍历，维护 first, second, third 就好、、、
class Solution(object):
def thirdMax(self, nums):
"""
:type nums: List[int]
:rtype: int
"""
nums = list(set(nums))
if len(nums) < 3:
return max(nums)
first, second, third = nums[0], nums[1], nums[2]
for num in nums:
if num > first:
first, second, third = num, first, second
elif num < first and num > second:
second, third = num, second
elif num > third and num < second:
third = num
return third
leetcode 448，噗！直接转集合做差集就好。
class Solution(object):
def findDisappearedNumbers(self, nums):
"""
:type nums: List[int]
:rtype: List[int]
"""
return list(set(range(1, len(nums) + 1)) - set(nums))
