human
Give me a the Python program you requested given the following:
I am working on the file "01_Sort.ipynb".
The first task is:
Third Maximum Number

Given a non-empty array of integers, return the third maximum number in this array. If it does not exist, return the maximum number. The time complexity must be in O(n).
Example 1:
Input: [3, 2, 1]
Output: 1
Explanation: The third maximum is 1.
Example 2:
Input: [1, 2]
Output: 2
Explanation: The third maximum does not exist, so the maximum (2) is returned instead.
Example 3:
Input: [2, 2, 3, 1]
Output: 1
Explanation: Note that the third maximum here means the third maximum distinct number.
Both numbers with value 2 are both considered as second maximum.
Can you write Python program for it?
assistant
#Here is the Python program you requested.

class Solution(object):
    def thirdMax(self, nums):
        """
        :type nums: List[int]
        :rtype: int
        """
        nums = set(nums)   ## this is important!!
        if len(nums) < 3:
            return max(nums)
        nums.remove(max(nums))
        nums.remove(max(nums))
        return max(nums)